V4L/DVB (9632): make em28xx aux audio input work

The attached patch makes the em28xx auxillary audio input work.
Tested with the HVR-950.

em28xx: make auxillary audio input work

The tuner audio input was working but the aux input wasn't.  Tested with
the HVR-950.

Signed-off-by: Devin Heitmueller <devin.heitmueller@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>