dt-bindings: devapc: add bindings for mtk-devapc

Add bindings for mtk-devapc.

Signed-off-by: Neal Liu <neal.liu@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1602732039-12179-2-git-send-email-neal.liu@mediatek.com


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