media: mt9m114: Add and use mt9m114_ifp_get_border() helper function

media: mt9m114: Add and use mt9m114_ifp_get_border() helper function

Normally the IFP removes a 4 pixel border all around its sink format
size for demosaicing. But in RAW10 mode it does not do this.

Add a new mt9m114_ifp_get_border() helper function to get the border size
(4 or 0) and use this where applicable instead of hardcoding a border
of 4 pixels everywhere.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>