V4L/DVB (9228): cx88: Add audio routing for the hvr-3000/4000

This adds audio routing on the hvr-3000/4000

This is a preliminary patch for later routing
requirements.

This adds line-in support on the 2 cards mentioned.
It is also apparent that there is an initial open
fault for line-in when opening composite/s-video.
This will be fixed later.

It was also noticed that the bit-field for audio
routing which was 2 bits needs an increase as
the WM8775 for example, allows a value 4 bits
wide for it's audio mux.

Signed-off-by: Darron Broad <darron@kewl.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>