drm: renesas: rz-du: Make DU reset control optional for RZ/T2H support

drm: renesas: rz-du: Make DU reset control optional for RZ/T2H support

Update the DU CRTC initialisation to request the reset control using
devm_reset_control_get_optional_shared(). On RZ/T2H SoCs the DU block does
not expose a reset line, and treating the reset as mandatory prevents the
driver from probing on those platforms.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://patch.msgid.link/20260519160825.4082566-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>