dt-bindings: pinctrl: rockchip: further increase max amount of device functions

Apparently RK3588 pinctrl has 13 different device functions, but dt-validate
only checks for pin configuration being referenced so I did not notice.

Fixes: ed1f77b7 ("dt-bindings: pinctrl: rockchip: increase max amount of device functions")
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20221021172012.87954-1-sebastian.reichel@collabora.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

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

@@ -132,7 +132,7 @@ additionalProperties:
               description:
                 Pin bank index.
             - minimum: 0
-              maximum: 10
+              maximum: 13
               description:
                 Mux 0 means GPIO and mux 1 to N means
                 the specific device function.