arm64: dts: meson: g12a: enable hdmi_tx sound dai provider

At the moment the sysnopsys hdmi i2s driver provides a single playback
DAI. Add the corresponding sound-dai-cell to the hdmi device node.
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-g12a.dtsi

@@ -158,6 +158,7 @@ hdmi_tx: hdmi-tx@0 {
 				clock-names = "isfr", "iahb", "venci";
 				#address-cells = <1>;
 				#size-cells = <0>;
+				#sound-dai-cells = <0>;
 				status = "disabled";
 
 				/* VPU VENC Input */