arm64: dts: mediatek: mt6795: Add tertiary PWM node

The PWM at 0x11006000 is the tertiary PWM; unlike PWM0, PWM1, this is
not display specific and can be used as a generic PWM controller.

This node is left disabled as usage is board-specific.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230412112739.160376-21-angelogioacchino.delregno@collabora.com


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