arm64: dts: rockchip: Enable HDMI audio on Rock Pi

This commit enables the hdmi-sound device needed to have
audio over HDMI on the Rock Pi board.

Fixes: 1b5715c6 ("arm64: dts: rockchip: add ROCK Pi 4 DTS support")
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4.dts

@@ -178,6 +178,10 @@ &hdmi {
 	status = "okay";
 };
 
+&hdmi_sound {
+	status = "okay";
+};
+
 &i2c0 {
 	clock-frequency = <400000>;
 	i2c-scl-rising-time-ns = <168>;