arm64: dts: rockchip: Support poweroff on Orange Pi 5

The RK806 on the Orange Pi 5 can be used to power on/off the whole board.
Mark it as the system power controller.

Signed-off-by: Jimmy Hon <honyuenkwun@gmail.com>
Link: https://lore.kernel.org/r/20231227203211.1047-1-honyuenkwun@gmail.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>