V4L/DVB: ngene: add initial support for digital side of Avermedia m780

Add ATSC/QAM support for the Avermedia m780.  Note that this patch does
not include any analog support for the board, as the ngene bridge driver does
not yet have analog implemented

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>