arm64: dts: mediatek: mt7622: Add missing pwm-cells to pwm node

Specify #pwm-cells on pwm@11006000 to make it actually usable.

Fixes: ae457b76 ("arm64: dts: mt7622: add SoC and peripheral related device nodes")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221128112028.58021-2-angelogioacchino.delregno@collabora.com


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