arm64: dts: rockchip: enable hdmi sound on rk3399-sapphire

Simply enable the hdmi-sound simple-audio-card on the
sapphire board.
Signed-off-by: Vicente Bergas <vicencb@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

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

@@ -190,6 +190,10 @@ &hdmi {
 	status = "okay";
 };
 
+&hdmi_sound {
+	status = "okay";
+};
+
 &i2c0 {
 	clock-frequency = <400000>;
 	i2c-scl-rising-time-ns = <168>;