dt-bindings: pinctrl: Add rk3506 pinctrl support

Add the compatible string for the rk3506 SoC.

Signed-off-by: Ye Zhang <ye.zhang@rock-chips.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Ye Zhang

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

@@ -44,6 +44,7 @@ properties:
       - rockchip,rk3328-pinctrl
       - rockchip,rk3368-pinctrl
       - rockchip,rk3399-pinctrl
+      - rockchip,rk3506-pinctrl
       - rockchip,rk3528-pinctrl
       - rockchip,rk3562-pinctrl
       - rockchip,rk3568-pinctrl