V4L/DVB (12336): ivtv: Fix improper GPIO audio mux input switch on video standard...

V4L/DVB (12336): ivtv: Fix improper GPIO audio mux input switch on video standard change

Remove the subdev_s_std() method from the GPIO subdev.  It appears it was
used in the past to effect the switch back from radio mode to tuner mode,
but it had a side effect that is improper and against the V4L2 spec, when
you were not in radio mode.  Whenever the video stanadrd was changed, the
GPIO audio mux was set back to the tuner audio input, even if you were set
to a Line In input.

Thanks to Ravi A. for doing the troubleshooting to point me right to the
problem.

Reported-by: Ravi A <asvravi@gmail.com>
Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>