media: staging: media: imx: imx7-media-csi: Fold capture_priv into imx7_csi

Merge the capture_priv fields in the imx7_csi structure as there's no
more need to have two separate structures. Update all the users
accordingly.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>