drm: renesas: rz-du: Implement MIPI DSI host transfers

drm: renesas: rz-du: Implement MIPI DSI host transfers

Add support for sending MIPI DSI command packets from the host to a
peripheral. This is required for panels that need configuration before
they accept video data.

Also for long reads to work properly, set DCS maximum return packet size
to the value of the DMA buffer size.

Based on Renesas Linux kernel v5.10 repos [1].
Link: https://github.com/renesas-rz/rz_linux-cip.git
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Tested-by: Chris Brandt <Chris.Brandt@renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20250604145306.1170676-2-hugo@hugovil.com