ARM: dts: sun9i: Add uart4 pinmux setting for A80 SoC

uart4 only has one possible pinmux setting on the A80 SoC.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun9i-a80.dtsi

@@ -365,6 +365,13 @@ uart0_pins_a: uart0@0 {
 				allwinner,drive = <0>;
 				allwinner,pull = <0>;
 			};
+
+			uart4_pins_a: uart4@0 {
+				allwinner,pins = "PG12", "PG13", "PG14", "PG15";
+				allwinner,function = "uart4";
+				allwinner,drive = <0>;
+				allwinner,pull = <0>;
+			};
 		};
 
 		uart0: serial@07000000 {