dt-bindings: power: Add support for MT8196 power controllers

dt-bindings: power: Add support for MT8196 power controllers

Add support for the power controllers found in the MediaTek MT8196
Chromebook SoC.

This chip has three power controllers, two of which located in the
SCP subsystems (where one can be directly controlled and the other
can be controlled only through the HW Voter IP), and one located
in the Multimedia HFRP subsystem, controllable only through the HW
Voter IP.

Acked-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>