dt-bindings: pinctrl: rockchip: add rk3588

Add compatible string for rk3588 pin controller. No other changes
are required, since the new controller can use the old binding.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20220422170920.401914-12-sebastian.reichel@collabora.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/rockchip,pinctrl.yaml

@@ -45,6 +45,7 @@ properties:
       - rockchip,rk3368-pinctrl
       - rockchip,rk3399-pinctrl
       - rockchip,rk3568-pinctrl
+      - rockchip,rk3588-pinctrl
       - rockchip,rv1108-pinctrl
 
   rockchip,grf: