dt-bindings: pinctrl: meson: Add compatible for S4

Add new compatible for Amlogic's Meson-S4 pin controller
Reviewed-by: NMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: NQianggui Song <qianggui.song@amlogic.com>
Link: https://lore.kernel.org/r/20220113031044.2665-2-qianggui.song@amlogic.comSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

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

@@ -16,6 +16,7 @@ Required properties for the root node:
 		      "amlogic,meson-g12a-periphs-pinctrl"
 		      "amlogic,meson-g12a-aobus-pinctrl"
 		      "amlogic,meson-a1-periphs-pinctrl"
+		      "amlogic,meson-s4-periphs-pinctrl"
  - reg: address and size of registers controlling irq functionality
 
 === GPIO sub-nodes ===