dt-bindings: power: rockchip: Add bindings for rk3588

Add the compatible string for RK3588 SoC.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20220906143825.199089-4-sebastian.reichel@collabora.com


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