ASoC: dt-bindings: sun50i-codec-analog: Add headphone amp regulator supply

On the Allwinner A64 SoC, the audio codec has a built-in headphone
amplifier. This amplifier has a power supply separate from the rest of
the analog audio circuitry.

Add a regulator supply property to handle this.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/sun50i-codec-analog.txt

@@ -4,9 +4,11 @@ Required properties:
 - compatible: must be one of the following compatibles:
 		- "allwinner,sun50i-a64-codec-analog"
 - reg: must contain the registers location and length
+- cpvdd-supply: Regulator supply for the headphone amplifier
 
 Example:
 	codec_analog: codec-analog@1f015c0 {
 		compatible = "allwinner,sun50i-a64-codec-analog";
 		reg = <0x01f015c0 0x4>;
+		cpvdd-supply = <&reg_eldo1>;
 	};