dt-bindings: watchdog: fsl-imx-wdt: Add missing 'big-endian' property

Add missing big-endian property in watchdog/fsl-imx-wdt.yaml schema. Only
allow big-endian property for ls1012a and ls1043a.

Fix dtbs_check errors.
arch/arm64/boot/dts/freescale/fsl-ls1012a-frwy.dtb: watchdog@2ad0000:
    Unevaluated properties are not allowed ('big-endian' was unexpected)

Cc: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Animesh Agarwal <animeshagarwal28@gmail.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Link: https://lore.kernel.org/r/20241007212434.895521-1-Frank.Li@nxp.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml

@@ -48,6 +48,8 @@ properties:
   clocks:
     maxItems: 1
 
+  big-endian: true
+
   fsl,ext-reset-output:
     $ref: /schemas/types.yaml#/definitions/flag
     description: |
@@ -93,6 +95,18 @@ allOf:
       properties:
         fsl,suspend-in-wait: false
 
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - fsl,ls1012a-wdt
+                - fsl,ls1043a-wdt
+    then:
+      properties:
+        big-endian: false
+
 unevaluatedProperties: false
 
 examples: