dt-bindings: pinctrl: rockchip: Document RV1126 pinctrl

Document dt-bindings for RV1126 SoC pinctrl support.

Cc: linux-gpio@vger.kernel.org
Cc: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20220818124132.125304-7-jagan@edgeble.ai


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>