[media] omap3isp: preview: Rename prev_params fields to match userspace API

Rename the blk_adj and rgb2ycbcr fields to blkadj and csc respectively.

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