drm: renesas: rz-du: Drop ARCH_RZG2L dependency

drm: renesas: rz-du: Drop ARCH_RZG2L dependency

The RZ/G2L DU driver is now also used on other Renesas SoCs such as
RZ/V2H(P) and RZ/V2N. Restricting it to ARCH_RZG2L prevents enabling it
on these newer platforms.

Replace the ARCH_RZG2L dependency with ARCH_RENESAS to allow the driver
to be built on all relevant Renesas SoCs.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20251002123452.146610-1-prabhakar.mahadev-lad.rj@bp.renesas.com