dt-bindings: watchdog: convert ziirave-wdt.txt to yaml

Convert ziirave-wdt.txt to yaml format.

Additional change:
- Add i2c node in example.
- Add ref to watchdog.yaml

Fix below warning:
arch/arm64/boot/dts/freescale/imx8mq-zii-ultra-rmb3.dtb: /soc@0/bus@30800000/i2c@30a40000/watchdog@38:
	failed to match any schema with compatible: ['zii,rave-wdt']
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240814161250.4017427-1-Frank.Li@nxp.comSigned-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/watchdog/zii,rave-wdt.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/zii,rave-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Zodiac RAVE Watchdog Timer
+
+maintainers:
+  - Martyn Welch <martyn.welch@collabora.co.uk>
+  - Guenter Roeck <linux@roeck-us.net>
+  - Wim Van Sebroeck <wim@iguana.be>
+
+properties:
+  compatible:
+    const: zii,rave-wdt
+
+  reg:
+    maxItems: 1
+    description: i2c slave address of device, usually 0x38
+
+  reset-duration-ms:
+    description:
+      Duration of the pulse generated when the watchdog times
+      out.
+
+required:
+  - compatible
+  - reg
+
+allOf:
+  - $ref: watchdog.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        watchdog@38 {
+            compatible = "zii,rave-wdt";
+            reg = <0x38>;
+            timeout-sec = <30>;
+            reset-duration-ms = <30>;
+        };
+    };
+

Documentation/devicetree/bindings/watchdog/ziirave-wdt.txt

-Zodiac RAVE Watchdog Timer
-
-Required properties:
-- compatible: must be "zii,rave-wdt"
-- reg: i2c slave address of device, usually 0x38
-
-Optional Properties:
-- timeout-sec: Watchdog timeout value in seconds.
-- reset-duration-ms: Duration of the pulse generated when the watchdog times
-  out. Value in milliseconds.
-
-Example:
-
-	watchdog@38 {
-		compatible = "zii,rave-wdt";
-		reg = <0x38>;
-		timeout-sec = <30>;
-		reset-duration-ms = <30>;
-	};