ASoC: dt-binding: Add bindings for Allwinner A64 codec's analog path controls

The internal codec on Allwinner A64 is split into 2 parts. The
analog path controls are routed through an embedded custom register
bus accessed through the PRCM block just as on A23/A33/H3.

Add a binding for this hardware.
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

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

+* Allwinner A64 Codec Analog Controls
+
+Required properties:
+- compatible: must be one of the following compatibles:
+		- "allwinner,sun50i-a64-codec-analog"
+- reg: must contain the registers location and length
+
+Example:
+	codec_analog: codec-analog@1f015c0 {
+		compatible = "allwinner,sun50i-a64-codec-analog";
+		reg = <0x01f015c0 0x4>;
+	};