media: sun6i-csi: Introduce bridge format structure, list and helper

Introduce a more informative format list for the bridge, with
information about how to configure the input. This separation will
later be useful when using the bridge standalone (without capture)
for the isp workflow.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>