V4L/DVB (3247): Replace AUDC_SET_INPUT with VIDIOC_S_AUDIO in wm8775.

- Replace AUDC_SET_INPUT with VIDIOC_S_AUDIO.
- Added V4L2_CID_AUDIO_MUTE.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>