drm: renesas: Add RZ/G2L DU Support

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

It has DPI/DSI interfaces and supports a maximum resolution of 1080p
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/G2L DU support for RZ/G2L
alike SoCs.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20240218164840.57662-4-biju.das.jz@bp.renesas.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>