ASoC: dio2125: add dt-bindings

Signed-off-by: NJerome Brunet <jbrunet@baylibre.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/dioo,dio2125.txt

+DIO2125 Audio Driver
+
+Required properties:
+- compatible : "dioo,dio2125"
+- enable-gpios : the gpio connected to the enable pin of the dio2125
+
+Example:
+
+amp: analog-amplifier {
+	compatible = "dioo,dio2125";
+	enable-gpios = <&gpio GPIOH_3 0>;
+};