V4L/DVB (3249): Generalized cx25840 video/audio input handling

- Added VIDIOC_S_AUDIO to set the audio inputs separately.
- Removed AUDC_SET_INPUT.
- Made the video inputs much more general.
- Removed cardtype CID and replaced with a CID to enable
the PVR150 workaround. The cardtype is no longer necessary
with the general video input change.
- Update VIDIOC_LOG_STATUS output to show the video and
audio inputs separately.

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