n_gsm : Flow control handling in Mux driver

commit c01af4fec2c8f303d6b3354d44308d9e6bef8026 upstream.

- Correcting handling of FCon/FCoff in order to respect 27.010 spec
- Consider FCon/off will overide all dlci flow control except for
  dlci0 as we must be able to send control frames.
- Dlci constipated handling according to FC, RTC and RTR values.
- Modifying gsm_dlci_data_kick and gsm_dlci_data_sweep according
  to dlci constipated value

Change-Id: Ibd6278bedcbeedaeb2faadc9a5e4521ce8aee547
Signed-off-by: Frederic Berat <fredericx.berat@intel.com>
Signed-off-by: Russ Gorby <russ.gorby@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
char: n_gsm: remove message filtering for contipated DLCI

commit 10c6c383e43565c9c6ec07ff8eb2825f8091bdf0 upstream.

The design of uplink flow control in the mux driver is
that for constipated channels data will backup into the
per-channel fifos, and any messages that make it to the
outbound message queue will still go out.
Code was added to also stop messages that were in the outbound
queue but this requires filtering through all the messages on the
queue for stopped dlcis and changes some of the mux logic unneccessarily.

The message fiiltering was removed to be in line w/ the original design
as the message filtering does not provide any solution.
Extra debug messages used during investigation were also removed.

Change-Id: I872cedc4c0e3651dacd89828c8d7e2129a8c37f7
Signed-off-by: samix.lebsir <samix.lebsir@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>