arm64: dts: mt8192: Add pwm node

Add pwm node for mt8192 SoC.

Signed-off-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20220712114046.15574-2-allen-kh.cheng@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>