ARM: sun8i: a83t: cubietruck-plus: Enable SPDIF output

The Cubietruck Plus has an optical SPDIF out connector.
Enable SPDIF audio output for this board.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun8i-a83t-cubietruck-plus.dts

@@ -82,6 +82,28 @@ green {
 			gpios = <&pio 4 4 GPIO_ACTIVE_HIGH>; /* PE4 */
 		};
 	};
+
+	sound {
+		compatible = "simple-audio-card";
+		simple-audio-card,name = "On-board SPDIF";
+
+		simple-audio-card,cpu {
+			sound-dai = <&spdif>;
+		};
+
+		simple-audio-card,codec {
+			sound-dai = <&spdif_out>;
+		};
+	};
+
+	spdif_out: spdif-out {
+		#sound-dai-cells = <0>;
+		compatible = "linux,spdif-dit";
+	};
+};
+
+&spdif {
+	status = "okay";
 };
 
 &uart0 {