dt-bindings: watchdog: renesas,wdt: Document RZ/G3S support

Document the support for the watchdog IP available on RZ/G3S SoC. The
watchdog IP available on RZ/G3S SoC is identical to the one found on
RZ/G2L SoC.

Signed-off-by: Claudiu Beznea <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

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

···
               - renesas,r9a07g043-wdt    # RZ/G2UL and RZ/Five
               - renesas,r9a07g044-wdt    # RZ/G2{L,LC}
               - renesas,r9a07g054-wdt    # RZ/V2L
+              - renesas,r9a08g045-wdt    # RZ/G3S
           - const: renesas,rzg2l-wdt
 
       - items: