dt-bindings: pinctrl: rockchip: add rk3308 SoC support

Add rk3308 SoC support to rockchip pinctrl.
Acked-by: NRob Herring <robh@kernel.org>
Reviewed-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NJianqun Xu <jay.xu@rock-chips.com>
Link: https://lore.kernel.org/r/20191015091708.7934-2-jay.xu@rock-chips.comSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

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

@@ -29,6 +29,7 @@ Required properties for iomux controller:
 		"rockchip,rk3188-pinctrl":  for Rockchip RK3188
 		"rockchip,rk3228-pinctrl":  for Rockchip RK3228
 		"rockchip,rk3288-pinctrl":  for Rockchip RK3288
+		"rockchip,rk3308-pinctrl":  for Rockchip RK3308
 		"rockchip,rk3328-pinctrl":  for Rockchip RK3328
 		"rockchip,rk3368-pinctrl":  for Rockchip RK3368
 		"rockchip,rk3399-pinctrl":  for Rockchip RK3399