dt-bindings: watchdog: renesas,wdt: R-Car V3U is R-Car Gen4

Despite the name, R-Car V3U is the first member of the R-Car Gen4
family. Hence move its compatible value to the R-Car Gen4 section.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Reviewed-by: Wolfram Sang <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/2882a[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,r8a77980-wdt     # R-Car V3H
               - renesas,r8a77990-wdt     # R-Car E3
               - renesas,r8a77995-wdt     # R-Car D3
-              - renesas,r8a779a0-wdt     # R-Car V3U
           - const: renesas,rcar-gen3-wdt # R-Car Gen3 and RZ/G2
 
       - items:
           - enum:
+              - renesas,r8a779a0-wdt     # R-Car V3U
               - renesas,r8a779f0-wdt     # R-Car S4-8
           - const: renesas,rcar-gen4-wdt # R-Car Gen4