V4L/DVB (3582): Implement correct msp3400 input/output routing

- implement VIDIOC_INT_S_AUDIO_ROUTING for msp3400 and tvaudio
- use the new command in bttv, pvrusb2 and em28xx.
- remove the now obsolete MSP_SET_MATRIX from msp3400 (yeah!)
- remove the obsolete VIDIOC_S_AUDIO from msp3400.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>