arm64: dts: mediatek: mt8188: Add missing #reset-cells property

The binding now require the '#reset-cells' property but the
devicetree has not been updated which trigger dtb-check errors.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Julien Massot <julien.massot@collabora.com>
Link: https://lore.kernel.org/r/20250516-dtb-check-mt8188-v2-2-fb60bef1b8e1@collabora.com


Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>