ARM: dts: sun8i: Add pin muxing option for R_UART

R_UART is available on extra pads on certain tablets, which makes it
ideal for use as a console. Here we add the pins for it.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun8i-a23.dtsi

@@ -378,6 +378,13 @@ r_pio: pinctrl@01f02c00 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 			#gpio-cells = <3>;
+
+			r_uart_pins_a: r_uart@0 {
+				allwinner,pins = "PL2", "PL3";
+				allwinner,function = "s_uart";
+				allwinner,drive = <0>;
+				allwinner,pull = <0>;
+			};
 		};
 	};
 };