V4L/DVB (6831): Audio routes fix for blackbird boards with the wm8775 ADC

Fix lack of audio on the MPEG-2 stream of wm8775 based blackbirds.

The wm8775 module initializes the audio input at "route 2", which doesn't
hold true for all boards. The HVR-1300, for example, uses route 1 for
tuner audio, and route 2 for baseband. So we must route the audio to the
proper input depending on what video input is being used.

Signed-off-by: Ricardo Cerqueira <v4l@cerqueira.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>