ARM: dts: sun6i: Add SPDIF TX pin to the A31

Add the SPDIF TX pin to the A31 dtsi.
Signed-off-by: Marcus Cooper <codekipper@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun6i-a31.dtsi

@@ -586,6 +586,11 @@ mmc3_8bit_emmc_pins: mmc3@1 {
 				bias-pull-up;
 			};
 
+			spdif_pins_a: spdif@0 {
+				pins = "PH28";
+				function = "spdif";
+			};
+
 			uart0_pins_a: uart0@0 {
 				pins = "PH20", "PH21";
 				function = "uart0";