dt-bindings: arm: rockchip: add rk5388 compatible string to pmu.yaml

Add the compatible for the pmu mfd on rk3588.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20220906143825.199089-2-sebastian.reichel@collabora.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/arm/rockchip/pmu.yaml

@@ -25,6 +25,7 @@ select:
           - rockchip,rk3368-pmu
           - rockchip,rk3399-pmu
           - rockchip,rk3568-pmu
+          - rockchip,rk3588-pmu
 
   required:
     - compatible
@@ -39,6 +40,7 @@ properties:
           - rockchip,rk3368-pmu
           - rockchip,rk3399-pmu
           - rockchip,rk3568-pmu
+          - rockchip,rk3588-pmu
       - const: syscon
       - const: simple-mfd