media: rzg2l-cru: csi2: Mark sink and source pad with MUST_CONNECT flag

media: rzg2l-cru: csi2: Mark sink and source pad with MUST_CONNECT flag

Mark the sink and source pad with the MEDIA_PAD_FL_MUST_CONNECT flag to
ensure pipeline validation fails if it is not connected.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20241018133446.223516-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>