dt-bindings: watchdog: renesas,wdt: Document RZ/V2N (R9A09G056) support

Document support for the watchdog IP found on the Renesas RZ/V2N
(R9A09G056) SoC. The watchdog IP is identical to that on RZ/V2H(P),
so `renesas,r9a09g057-wdt` will be used as a fallback compatible,
enabling reuse of the existing driver without changes.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20250502120054.47323-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Author: prabhakarlad

Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml

@@ -76,7 +76,9 @@ properties:
           - const: renesas,rcar-gen4-wdt # R-Car Gen4
 
       - items:
-          - const: renesas,r9a09g047-wdt # RZ/G3E
+          - enum:
+              - renesas,r9a09g047-wdt # RZ/G3E
+              - renesas,r9a09g056-wdt # RZ/V2N
           - const: renesas,r9a09g057-wdt # RZ/V2H(P)
 
       - const: renesas,r9a09g057-wdt       # RZ/V2H(P)