dt-bindings: watchdog: loongson,ls1x-wdt: Add ls2k0300-wdt compatible

Add "loongson,ls2k0300-wdt" compatible to the dt-schema document, which
is similar to Loongson-1 watchdog, but with differences in some register
offsets and bit definitions.

Signed-off-by: Binbin Zhou <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
pw-bot: not-applicable
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

Documentation/devicetree/bindings/watchdog/loongson,ls1x-wdt.yaml

···
 $id: http://devicetree.org/schemas/watchdog/loongson,ls1x-wdt.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: Loongson-1 Watchdog Timer
+title: Loongson Watchdog Timer
 
 maintainers:
   - Keguang Zhang <[e-mail]>
···
     enum:
       - loongson,ls1b-wdt
       - loongson,ls1c-wdt
+      - loongson,ls2k0300-wdt
 
   reg:
     maxItems: 1