ti-st: tty_hci: Remove redundant assignment.

Clean up for the code: remove redundant assignment.

Change-Id: I595b549fedec4c89177f342c957e95668f184442
Signed-off-by: Oleksandr Kozaruk <oleksandr.kozaruk@ti.com>
ti-st: tty_hci: Fix race condition in hci_tty_open.

Race condition is possible in the hci_tty driver.
The race result in NULL pointer dereference due to
struct sk_buff_head rx_list is used without prior
initialization.

The error condition can easily reproduced with the script
and COM-7 wilink hardware module:
while [ 1 ]; do echo -n "fail" > /dev/nfc; sleep 2; done

[   56.229614] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[   56.238494] pgd = c0004000
[   56.241485] [00000000] *pgd=00000000
[   56.245513] Internal error: Oops: 805 [#1] PREEMPT SMP ARM
[   56.251586] Modules linked in: rproc_drm(O) tf_driver(O) gps_drv wl18xx(O) wl12xx(O) wlcore(O) mac80211(O) pvrsrvkm_sgx544_112(O) cfg80211(O) compat(O) [last unloaded: wlcore_sdio]
[   56.270141] CPU: 0    Tainted: G        W  O  (3.4.34-01546-g66a9034 #82)
[   56.277618] PC is at skb_queue_tail+0x2c/0x50
[   56.282409] LR is at _raw_spin_lock_irqsave+0x10/0x14
[   56.287994] pc : [<c04eeb04>]    lr : [<c0686618>]    psr: 60000193
[   56.287994] sp : d6cbde60  ip : d6cbde50  fp : d6cbde7c
[   56.300628] r10: d6ecf5d4  r9 : d6ecf558  r8 : 00000000
[   56.306335] r7 : d6ecf5ac  r6 : cb78347c  r5 : d67c6500  r4 : cb783470
[   56.313537] r3 : 00000000  r2 : a0000193  r1 : d67c6500  r0 : a0000193
[   56.320648] Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
[   56.328796] Control: 10c5387d  Table: 8b6a804a  DAC: 00000015
       [skiped ...]
[   57.452667] Backtrace:
[   57.455474] [<c04eead8>] (skb_queue_tail+0x0/0x50) from [<c0300bec>] (st_receive+0x18/0x34)
[   57.464630]  r6:d5920c59 r5:00000004 r4:cb783440 r3:c0300bd4
[   57.471191] [<c0300bd4>] (st_receive+0x0/0x34) from [<c02fe924>] (st_send_frame+0x50/0xac)
[   57.480255]  r4:d6ecf540 r3:c0300bd4
[   57.484344] [<c02fe8d4>] (st_send_frame+0x0/0xac) from [<c02ff13c>] (st_int_recv+0x1fc/0x3a0)
[   57.493713]  r5:00000000 r4:d6ecf540
[   57.497894] [<c02fef40>] (st_int_recv+0x0/0x3a0) from [<c02fe548>] (st_tty_receive+0x24/0x28)
[   57.507171] [<c02fe524>] (st_tty_receive+0x0/0x28) from [<c02bbac0>] (flush_to_ldisc+0x150/0x1b4)
[   57.516906] [<c02bb970>] (flush_to_ldisc+0x0/0x1b4) from [<c0061950>] (process_one_work+0x134/0x4ac)
[   57.526916] [<c006181c>] (process_one_work+0x0/0x4ac) from [<c0061e54>] (worker_thread+0x18c/0x3d8)
[   57.536865] [<c0061cc8>] (worker_thread+0x0/0x3d8) from [<c00668d0>] (kthread+0x90/0x9c)
[   57.545684] [<c0066840>] (kthread+0x0/0x9c) from [<c004a8a8>] (do_exit+0x0/0x804)
[   57.553894]  r6:c004a8a8 r5:c0066840 r4:d6c5dec4

Change-Id: Ife34d53b4fad45d1db600d71450b06dce0328b2c
Signed-off-by: Oleksandr Kozaruk <oleksandr.kozaruk@ti.com>
ti-st: tty_hci: Properly unregister protocols in open.

In case of error condition registered protocols were not
unregistered from st core when open syscall was called. Memory
allocated for the driver data was just freed. Then callback
from st_register() called st_reg_complete_cb, and complete()
had the argument from the already freed memory.

This could be the reason of the null pointer dereference, as in
the log below. The issue is rarely reproduced.

[  132.189086] (stc): st_register(12)
[  132.198394] (stc):  chnl_id list empty :12
[  132.205352] (stk) : st_kim_start
[  132.329040] (stk) :ldisc_install = 1
[  133.087829] mtp_open
[  133.329010] (stk) :ldisc installation timeout
[  133.334960] (stk) :ldisc_install = 0
[  134.336853] (stk) : timed out waiting for ldisc to be un-installed
[  134.463165] (stk) :ldisc_install = 1
[  135.469757] (stk) :ldisc installation timeout
[  135.474334] (stk) :ldisc_install = 0
[  135.557830] init: sys_prop: permission denied uid:1003 name:service.bootanim.exit
[  135.653076] init: Boot Animation exit
[  135.895965] (hci_tty): inside hci_tty_open (d66bce38, d66ff480)
[  135.902435] (stc): st_register(4)
[  135.906494] (stc):  ST_REG_IN_PROGRESS:4
[  135.910858] (stc): add_channel_to_table: id 4
[  136.477478] (stk) : timed out waiting for ldisc to be un-installed
[  136.594635] (stk) :ldisc_install = 1
[  137.595001] (stk) :ldisc installation timeout
[  137.603759] (stk) :ldisc_install = 0
[  138.602508] (stk) : timed out waiting for ldisc to be un-installed
[  138.727478] (stk) :ldisc_install = 1
[  139.727722] (stk) :ldisc installation timeout
[  139.733734] (stk) :ldisc_install = 0
[  140.580657] binder: release 1324:1324 transaction 19588 out, still active
[  140.735321] (stk) : timed out waiting for ldisc to be un-installed
[  140.852447] (stk) :ldisc_install = 1
[  141.852478] (stk) :ldisc installation timeout
[  141.857360] (stk) :ldisc_install = 0
[  141.914978] (hci_tty): Timeout(6 sec),didn't get reg completion signal from ST
[  142.868072] (stk) : timed out waiting for ldisc to be un-installed
[  142.985382] (stk) :ldisc_install = 1
[  143.985351] (stk) :ldisc installation timeout
[  143.991546] (stk) :ldisc_install = 0
[  144.993072] (stk) : timed out waiting for ldisc to be un-installed
[  145.002960] (stc):  KIM failure complete callback
[  145.008392] (stc):  st_reg_complete
[  145.012725] (hci_tty): @ st_reg_completion_cb
[  145.017639] Unable to handle kernel NULL pointer dereference at virtual address 00000010
[  145.026428] pgd = c7cc0000
[  145.029388] [00000010] *pgd=00000000
[  145.033386] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
[  145.039215] Modules linked in: rproc_drm(O) tf_driver(O) gps_drv wl18xx(O) wl12xx(O) wlcore(O) mac80211(O) cfg80211(O) pvrsrvkm_sgx540_120(O) compat(O)
[  145.054870] CPU: 1    Tainted: G        W  O  (3.4.34 #1)
[  145.060821] PC is at __wake_up_common+0x2c/0x94
[  145.065734] LR is at complete+0x4c/0x60
[  145.069915] pc : [<c006ee4c>]    lr : [<c0070378>]    psr: a0000093
         [skiped...]
[  146.023742] Backtrace:
[  146.026550] [<c006ee20>] (__wake_up_common+0x0/0x94) from [<c0070378>] (complete+0x4c/0x60)
[  146.035644] [<c007032c>] (complete+0x0/0x60) from [<c0301f20>] (st_reg_completion_cb+0x30/0x38)
[  146.045104]  r6:d6ef5cd0 r5:00000092 r4:d617dd40
[  146.050384] [<c0301ef0>] (st_reg_completion_cb+0x0/0x38) from [<c02ffd34>] (st_reg_complete+0x60/0xa8)
[  146.060516]  r5:d6ef5cc4 r4:00000004
[  146.064575] [<c02ffcd4>] (st_reg_complete+0x0/0xa8) from [<c02fffac>] (st_register+0x230/0x324)
[  146.074066] [<c02ffd7c>] (st_register+0x0/0x324) from [<c0323cac>] (nfc_drv_open+0xe8/0x1e4)
[  146.083251]  r7:c8ec3840 r6:c0a5f89c r5:00000000 r4:c6016140
[  146.089752] [<c0323bc4>] (nfc_drv_open+0x0/0x1e4) from [<c0117aec>] (chrdev_open+0x9c/0x164)
[  146.098937] [<c0117a50>] (chrdev_open+0x0/0x164) from [<c0111b88>] (__dentry_open+0x200/0x2b8)
[  146.108306]  r8:c0117a50 r7:d66b1b28 r6:d5e1e910 r5:d69806f0 r4:c8ec3840
[  146.115997] [<c0111988>] (__dentry_open+0x0/0x2b8) from [<c0112c24>] (nameidata_to_filp+0x68/0x70)
[  146.125701] [<c0112bbc>] (nameidata_to_filp+0x0/0x70) from [<c01211ac>] (do_last.isra.20+0x150/0x6d4)
[  146.135711]  r7:00000026 r6:00000000 r5:00020002 r4:c6ccfed8
[  146.142272] [<c012105c>] (do_last.isra.20+0x0/0x6d4) from [<c0121954>] (path_openat+0xc0/0x3b8)
[  146.151672] [<c0121894>] (path_openat+0x0/0x3b8) from [<c0121d5c>] (do_filp_open+0x34/0x88)
[  146.160766] [<c0121d28>] (do_filp_open+0x0/0x88) from [<c0112d20>] (do_sys_open+0xf4/0x18c)
[  146.169830]  r7:00000001 r6:00000027 r5:00020002 r4:d63d1000
[  146.176330] [<c0112c2c>] (do_sys_open+0x0/0x18c) from [<c0112de0>] (sys_open+0x28/0x2c)
[  146.185058] [<c0112db8>] (sys_open+0x0/0x2c) from [<c0013680>] (ret_fast_syscall+0x0/0x30)
[  146.194061] Code: e1a08003 e50b2030 e157000c e59b9004 (e41c400c)
[

Change-Id: I10085ef1b1bc91ce3be01e179aa995287af271f1
Signed-off-by: Oleksandr Kozaruk <oleksandr.kozaruk@ti.com>