dt-bindings: power: supply: lego-ev3-battery: Convert to DT schema format

Convert the binding to DT schema format.

Cc: David Lechner <david@lechnology.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: David Lechner <david@lechnology.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/power/supply/lego,ev3-battery.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/power/supply/lego,ev3-battery.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: LEGO MINDSTORMS EV3 Battery
+
+maintainers:
+  - David Lechner <david@lechnology.com>
+  - Sebastian Reichel <sre@kernel.org>
+
+description: |
+  LEGO MINDSTORMS EV3 has some built-in capability for monitoring the battery.
+  It uses 6 AA batteries or a special Li-ion rechargeable battery pack that is
+  detected by a key switch in the battery compartment.
+
+allOf:
+  - $ref: power-supply.yaml#
+
+properties:
+  compatible:
+    const: lego,ev3-battery
+
+  io-channels:
+    items:
+      - description: ADC channel for battery voltage
+      - description: ADC channel for battery current
+
+  io-channel-names:
+    items:
+      - const: voltage
+      - const: current
+
+  rechargeable-gpios:
+    maxItems: 1
+    description: Rechargeable battery indication gpio
+
+required:
+  - compatible
+  - io-channels
+  - io-channel-names
+  - rechargeable-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    battery {
+      compatible = "lego,ev3-battery";
+      io-channels = <&adc 4>, <&adc 3>;
+      io-channel-names = "voltage", "current";
+      rechargeable-gpios = <&gpio 136 GPIO_ACTIVE_LOW>;
+    };

Documentation/devicetree/bindings/power/supply/lego_ev3_battery.txt

-LEGO MINDSTORMS EV3 Battery
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-LEGO MINDSTORMS EV3 has some built-in capability for monitoring the battery.
-It uses 6 AA batteries or a special Li-ion rechargeable battery pack that is
-detected by a key switch in the battery compartment.
-
-Required properties:
- - compatible: Must be "lego,ev3-battery"
- - io-channels: phandles to analog inputs for reading voltage and current
- - io-channel-names: Must be "voltage", "current"
- - rechargeable-gpios: phandle to the rechargeable battery indication gpio
-
-Example:
-
-	battery {
-		compatible = "lego,ev3-battery";
-		io-channels = <&adc 4>, <&adc 3>;
-		io-channel-names = "voltage", "current";
-		rechargeable-gpios = <&gpio 136 GPIO_ACTIVE_LOW>;
-	};