dt-bindings: watchdog: convert zii,rave-sp-wdt.txt to yaml format

Convert device binding doc zii,rave-sp-wdt.txt to yaml format.
Additional changes:
- Ref to watchdog.yaml.
- Remove mfd node in example.
- Remove eeprom part in example.

Signed-off-by: Frank Li <[e-mail]>
Reviewed-by: Rob Herring (Arm) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring (Arm) <[e-mail]>

Documentation/devicetree/bindings/watchdog/zii,rave-sp-wdt.txt

···
-Zodiac Inflight Innovations RAVE Supervisory Processor Watchdog Bindings
-
-RAVE SP watchdog device is a "MFD cell" device corresponding to
-watchdog functionality of RAVE Supervisory Processor. It is expected
-that its Device Tree node is specified as a child of the node
-corresponding to the parent RAVE SP device (as documented in
-Documentation/devicetree/bindings/mfd/zii,rave-sp.txt)
-
-Required properties:
-
-- compatible: Depending on wire protocol implemented by RAVE SP
-  firmware, should be one of:
-	- "zii,rave-sp-watchdog"
-	- "zii,rave-sp-watchdog-legacy"
-
-Optional properties:
-
-- wdt-timeout:	Two byte nvmem cell specified as per
-		Documentation/devicetree/bindings/nvmem/nvmem.txt
-
-Example:
-
-	rave-sp {
-		compatible = "zii,rave-sp-rdu1";
-		current-speed = <38400>;
-
-		eeprom {
-			wdt_timeout: wdt-timeout@8E {
-				reg = <0x8E 2>;
-			};
-		};
-
-		watchdog {
-			compatible = "zii,rave-sp-watchdog";
-			nvmem-cells = <&wdt_timeout>;
-			nvmem-cell-names = "wdt-timeout";
-		};
-	}
-

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

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/zii,rave-sp-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Zodiac Inflight Innovations RAVE Supervisory Processor Watchdog
+
+maintainers:
+  - Frank Li <[e-mail]>
+
+description:
+  RAVE SP watchdog device is a "MFD cell" device corresponding to
+  watchdog functionality of RAVE Supervisory Processor. It is expected
+  that its Device Tree node is specified as a child of the node
+  corresponding to the parent RAVE SP device (as documented in
+  Documentation/devicetree/bindings/mfd/zii,rave-sp.yaml)
+
+properties:
+  compatible:
+    enum:
+      - zii,rave-sp-watchdog
+      - zii,rave-sp-watchdog-legacy
+
+  nvmem-cell-names:
+    items:
+      - const: wdt_timeout
+
+  nvmem-cells:
+    maxItems: 1
+
+required:
+  - compatible
+
+allOf:
+  - $ref: watchdog.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    watchdog {
+        compatible = "zii,rave-sp-watchdog";
+        nvmem-cells = <&wdt_timeout>;
+        nvmem-cell-names = "wdt_timeout";
+    };
+