drm: renesas: rz-du: Increase supported resolutions

The supported resolutions were misrepresented in earlier versions of
hardware manuals.

Fixes: 768e9e61 ("drm: renesas: Add RZ/G2L DU Support")
Cc: stable@vger.kernel.org
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Tested-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241120150328.4131525-1-chris.brandt@renesas.com