dt-bindings: power: Add MT8192 power domains

Add power domains dt-bindings for MT8192.

Signed-off-by: Weiyi Lu <weiyi.lu@mediatek.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201030113622.201188-15-enric.balletbo@collabora.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>