dt-bindings: serial: amlogic, meson-uart: support S4

Add serial bindings support menson S4 SoC family.
Signed-off-by: NXianwei Zhao <xianwei.zhao@amlogic.com>
Link: https://lore.kernel.org/r/20211221030146.522-1-xianwei.zhao@amlogic.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml

@@ -29,6 +29,7 @@ properties:
               - amlogic,meson8-uart
               - amlogic,meson8b-uart
               - amlogic,meson-gx-uart
+              - amlogic,meson-s4-uart
           - const: amlogic,meson-ao-uart
       - description: Everything-Else power domain UART controller
         enum:
@@ -36,6 +37,7 @@ properties:
           - amlogic,meson8-uart
           - amlogic,meson8b-uart
           - amlogic,meson-gx-uart
+          - amlogic,meson-s4-uart
 
   reg:
     maxItems: 1