media: rzg2l-cru: Use RZG2L_CRU_IP_SINK/SOURCE enum entries

media: rzg2l-cru: Use RZG2L_CRU_IP_SINK/SOURCE enum entries

Use enum values (`RZG2L_CRU_IP_SINK` and `RZG2L_CRU_IP_SOURCE`) instead
of hardcoded array indices.

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/20241018133446.223516-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>