[media] omap3isp: Support additional in-memory compressed bayer formats

This also prevents accessing NULL pointer in csi2_try_format().

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>