media: sun6i-csi: Remove custom format helper and rework configure

Remove the custom sun6i_csi_get_bpp helper in favor of common v4l2
infrastructure and rework the related window configuration code.

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>