drm/i2c: tda998x: add video and audio input configuration

This patch adds tda998x specific parameters to allow it to be configured
for different boards using it. Also, this implements rudimentary audio
support for S/PDIF attached controllers.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Darren Etheridge <detheridge@ti.com>
Tested-by: Russell King <rmk_kernel@arm.linux.org.uk>
Tested-by: Russell King <rmk_kernel@arm.linux.org.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>