arm64: dts: rockchip: connect hdmi sound in rk3399

Everything is in place and working, it only needed to be wired up.
Signed-off-by: Vicente Bergas <vicencb@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399.dtsi

@@ -1520,6 +1520,7 @@ i2s2: i2s@ff8a0000 {
 		clock-names = "i2s_clk", "i2s_hclk";
 		clocks = <&cru SCLK_I2S2_8CH>, <&cru HCLK_I2S2_8CH>;
 		power-domains = <&power RK3399_PD_SDIOAUDIO>;
+		#sound-dai-cells = <0>;
 		status = "disabled";
 	};
 
@@ -1661,6 +1662,21 @@ isp1_mmu: iommu@ff924000 {
 		status = "disabled";
 	};
 
+	hdmi_sound: hdmi-sound {
+		compatible = "simple-audio-card";
+		simple-audio-card,format = "i2s";
+		simple-audio-card,mclk-fs = <256>;
+		simple-audio-card,name = "hdmi-sound";
+		status = "disabled";
+
+		simple-audio-card,cpu {
+			sound-dai = <&i2s2>;
+		};
+		simple-audio-card,codec {
+			sound-dai = <&hdmi>;
+		};
+	};
+
 	hdmi: hdmi@ff940000 {
 		compatible = "rockchip,rk3399-dw-hdmi";
 		reg = <0x0 0xff940000 0x0 0x20000>;
@@ -1674,6 +1690,7 @@ hdmi: hdmi@ff940000 {
 		power-domains = <&power RK3399_PD_HDCP>;
 		reg-io-width = <4>;
 		rockchip,grf = <&grf>;
+		#sound-dai-cells = <0>;
 		status = "disabled";
 
 		ports {