arm64: dts: mediatek: mt8183-evb: add PWM support

Enable the pwm driver and set the pinctrl for PWM A line.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Link: https://lore.kernel.org/r/20201209120322.137610-2-fparent@baylibre.com


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