dt-bindings: soc: rockchip: add rk3588 usb2phy syscon

The usb2phy is accessible via a syscon registers on RK3588, similar
to rk3399.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230403202307.120562-2-sebastian.reichel@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Author: sre

Documentation/devicetree/bindings/soc/rockchip/grf.yaml

@@ -52,6 +52,7 @@ properties:
               - rockchip,rk3399-pmugrf
               - rockchip,rk3568-grf
               - rockchip,rk3568-pmugrf
+              - rockchip,rk3588-usb2phy-grf
               - rockchip,rv1108-grf
               - rockchip,rv1108-pmugrf
               - rockchip,rv1126-grf
@@ -199,6 +200,7 @@ allOf:
               - rockchip,rk3308-usb2phy-grf
               - rockchip,rk3328-usb2phy-grf
               - rockchip,rk3399-grf
+              - rockchip,rk3588-usb2phy-grf
               - rockchip,rv1108-grf
 
     then: