dt-bindings: watchdog: add support for Amlogic A4 SoCs

Update dt-binding document for watchdog of Amlogic A4 SoCs.
Signed-off-by: Huqiang Qin <huqiang.qin@amlogic.com>
Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240709-a4-a5_watchdog-v1-1-2ae852e05ec2@amlogic.comSigned-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/watchdog/amlogic,meson-gxbb-wdt.yaml

@@ -21,6 +21,7 @@ properties:
           - amlogic,t7-wdt
       - items:
           - enum:
+              - amlogic,a4-wdt
               - amlogic,c3-wdt
               - amlogic,s4-wdt
           - const: amlogic,t7-wdt