Adjust the left crop of 720x480 to enable capture in RGB888 format,
which is otherwise broken.

The 56 pixels alignment has been copied from the 720x576 mode.
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>