drm: renesas: rz-du: Add RZ/G2UL DU Support

The LCD controller is composed of Frame Compression Processor (FCPVD),
Video Signal Processor (VSPD), and Display Unit (DU).

It has DPI interface and supports a maximum resolution of WXGA along
with 2 RPFs to support the blending of two picture layers and raster
operations (ROPs).

The DU module is connected to VSPD. Add RZ/G2UL DU support.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240822162320.5084-3-biju.das.jz@bp.renesas.com