dt-bindings:iio:dac:dpot-dac: yaml conversion.

Txt to yaml format conversion.  I dropped the example section
describing the measurement ADC, as that isn't strictly part
of this binding.

Uses the new dt-schema/schema/iio/iio-consumer.yaml schema.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20201031181242.742301-3-jic23@kernel.org

Documentation/devicetree/bindings/iio/dac/dpot-dac.txt

-Bindings for DAC emulation using a digital potentiometer
-
-It is assumed that the dpot is used as a voltage divider between the
-current dpot wiper setting and the maximum resistance of the dpot. The
-divided voltage is provided by a vref regulator.
-
-                  .------.
-   .-----------.  |      |
-   | vref      |--'    .---.
-   | regulator |--.    |   |
-   '-----------'  |    | d |
-                  |    | p |
-                  |    | o |  wiper
-                  |    | t |<---------+
-                  |    |   |
-                  |    '---'       dac output voltage
-                  |      |
-                  '------+------------+
-
-Required properties:
-- compatible: Should be "dpot-dac"
-- vref-supply: The regulator supplying the voltage divider.
-- io-channels: Channel node of the dpot to be used for the voltage division.
-- io-channel-names: Should be "dpot".
-
-Example:
-
-	&i2c {
-		dpot: mcp4651-503@28 {
-			compatible = "microchip,mcp4651-503";
-			reg = <0x28>;
-			#io-channel-cells = <1>;
-		};
-	};
-
-	dac {
-		compatible = "dpot-dac";
-		vref-supply = <&reg_3v3>;
-		io-channels = <&dpot 0>;
-		io-channel-names = "dpot";
-	};

Documentation/devicetree/bindings/iio/dac/dpot-dac.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/dac/dpot-dac.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: DAC emulation using a digital potentiometer
+
+maintainers:
+  - Peter Rosin <peda@axentia.se>
+
+description: |
+  It is assumed that the dpot is used as a voltage divider between the
+  current dpot wiper setting and the maximum resistance of the dpot. The
+  divided voltage is provided by a vref regulator.
+
+                  .------.
+   .-----------.  |      |
+   | vref      |--'    .---.
+   | regulator |--.    |   |
+   '-----------'  |    | d |
+                  |    | p |
+                  |    | o |  wiper
+                  |    | t |<---------+
+                  |    |   |
+                  |    '---'       dac output voltage
+                  |      |
+                  '------+------------+
+
+properties:
+  compatible:
+    const: dpot-dac
+
+  vref-supply:
+    description: Regulator supplying the voltage divider.
+
+  io-channels:
+    maxItems: 1
+    description: |
+      Channel node of the dpot to be used for the voltage division.
+
+  io-channel-names:
+    const: dpot
+
+  "#io-channel-cells":
+    const: 1
+
+required:
+  - compatible
+  - vref-supply
+  - io-channels
+  - io-channel-names
+
+additionalProperties: false
+
+examples:
+  - |
+    dac {
+        compatible = "dpot-dac";
+        vref-supply = <&reg_3v3>;
+        io-channels = <&dpot 0>;
+        io-channel-names = "dpot";
+    };
+...