[media] adv7180: Prepare for multi-chip support

The adv7180 is part of a larger family of device, which have all a very
similar register map layout. This patch prepares the adv7180 driver for
support for multiple different devices. For now the only difference we care
about is the number of input channel configurations. Also the way the input
format is configured slightly differs between some devices.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Federico Vaga <federico.vaga@gmail.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>