arm64: dts: mediatek: mt8183: add pwm node

MT8183 SoC has 4 PWMs. Add the pwm node in order to support them.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Link: https://lore.kernel.org/r/20201209120322.137610-1-fparent@baylibre.com


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