media: sun6i-csi: Rework capture format management with helper

Remove the need for local copies of the v4l2 format and add a common
helper to prepare a format compatible with the driver, using the
relevant v4l2 helpers.

Report a raw colorspace for bayer-encoded pixel formats instead of SRGB.
Also cleanup the size bound defines while at it.

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>