arm64: dts: mediatek: mt8188: Add PWM nodes for display backlight

arm64: dts: mediatek: mt8188: Add PWM nodes for display backlight

Add two hardware PWM nodes for display backlight usage on MT8188 SoC,
and mark them as disabled by default.
Boards can enable the necessary PWM node as needed.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://lore.kernel.org/r/20240911143429.850071-6-fshao@chromium.org
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>