media: rkisp1: Convert hex constants to lowercase

Hex constants in the media subsystem are typically in lowercase. The
rkisp1 driver mostly follows that convention already, except in the
register definitions. Convert all hex constants to lowercase for
consistency.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>