soc: mediatek: add header files required for MT7622 SCPSYS dt-binding

Add relevant header files required for dt-bindings of SCPSYS power domain
control for all subsystems found on MT7622 SoC.

Signed-off-by: Chen Zhong <chen.zhong@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>