mwl8787: simplify disable_host_int and rename to match enable

Using the magic of the "x & 0 = 0" identity, we're just writing
a zero to that register.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
mwl8787: turn off packet reception when stopped

Fixes this warning:
[ 7586.322889] ------------[ cut here ]------------
[ 7586.322907] WARNING: at net/mac80211/rx.c:3264
ieee80211_rx+0x77/0x78b [mac80211]()
[ 7586.322908] Modules linked in: mwl8787_sdio(-) parport_pc ppdev lp
parport bnep rfcomm binfmt_misc uinput nfsd nfs_acl nfs fscache lockd
sunrpc loop fuse snd_hda_codec_hdmi snd_hda_codec_realtek joydev
iTCO_wdt iTCO_vendor_support btusb arc4 bluetooth cdc_ncm coretemp
usbnet kvm_intel iwldvm mii cdc_acm kvm mac80211 cdc_wdm evdev psmouse
snd_hda_intel serio_raw snd_hda_codec iwlwifi pcspkr snd_hwdep snd_pcm
snd_page_alloc cfg80211 i915 thinkpad_acpi snd_seq snd_timer nvram
i2c_i801 snd_seq_device lpc_ich rfkill mfd_core battery snd tpm_tis ac
tpm tpm_bios soundcore i2c_algo_bit drm_kms_helper drm acpi_cpufreq
mperf i2c_core wmi video button processor ext4 mbcache crc16 jbd2
dm_crypt dm_mod sg sd_mod crc_t10dif crc32c_intel ghash_clmulni_intel
aesni_intel aes_x86_64 ablk_helper cryptd lrw gf128mul glue_helper ahci
libahci libata sdhci_pci sdhci scsi_mod ehci_pci xhci_hcd ehci_hcd
mmc_core usbcore thermal usb_common thermal_sys [last unloaded:
mwl8787_sdio]
[ 7586.322979] CPU: 0 PID: 3 Comm: ksoftirqd/0 Tainted: G        W
3.10.0+ #64
[ 7586.322980] Hardware name: LENOVO 3443CTO/3443CTO, BIOS G6ET23WW
(1.02 ) 08/14/2012
[ 7586.322982]  0000000000000002 ffff8801196f9c68 ffffffff813b827e
ffff8801196f9ca0
[ 7586.322985]  ffffffff81032dd4 0000000000000000 ffff8800308d8a60
ffff88005eaa1dc0
[ 7586.322988]  ffff8800308d8cf0 0000000000000100 ffff8801196f9cb0
ffffffff81032e06
[ 7586.322992] Call Trace:
[ 7586.322997]  [<ffffffff813b827e>] dump_stack+0x19/0x1b
[ 7586.323000]  [<ffffffff81032dd4>] warn_slowpath_common+0x65/0x7d
[ 7586.323002]  [<ffffffff81032e06>] warn_slowpath_null+0x1a/0x1c
[ 7586.323015]  [<ffffffffa051d6b6>] ieee80211_rx+0x77/0x78b [mac80211]
[ 7586.323020]  [<ffffffff8108147a>] ?
trace_hardirqs_on_caller+0x19e/0x1ad
[ 7586.323024]  [<ffffffff813bc602>] ?
_raw_spin_unlock_irqrestore+0x60/0x6e
[ 7586.323032]  [<ffffffffa04fe8cf>] ieee80211_tasklet_handler+0x3f/0xa6
[mac80211]
[ 7586.323036]  [<ffffffff8103aae0>] tasklet_action+0x86/0xdd
[ 7586.323039]  [<ffffffff8103a626>] __do_softirq+0x137/0x2a1
[ 7586.323042]  [<ffffffff8103a7b3>] run_ksoftirqd+0x23/0x53
[ 7586.323044]  [<ffffffff8105b5d9>] smpboot_thread_fn+0x242/0x260
[ 7586.323047]  [<ffffffff8105b397>] ?
test_ti_thread_flag.constprop.2+0x11/0x11
[ 7586.323049]  [<ffffffff8105422d>] kthread+0xb1/0xb9
[ 7586.323052]  [<ffffffff8105417c>] ? __kthread_parkme+0x65/0x65
[ 7586.323055]  [<ffffffff813c2edc>] ret_from_fork+0x7c/0xb0
[ 7586.323057]  [<ffffffff8105417c>] ? __kthread_parkme+0x65/0x65
[ 7586.323059] ---[ end trace 8ae6d6e6cc59345f ]---

Signed-off-by: Bob Copeland <me@bobcopeland.com>