media: rkisp1: Constify rkisp1_v12_params_ops

The rkisp1_v12_params_ops global variable doesn't need to be modified.
Make it const.

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>