dt-bindings: watchdog: renesas-wdt: Add support for the R8A77990 wdt

Document support for the Watchdog Timer (WDT) Controller in the Renesas
R-Car E3 (R8A77990) SoC.

No driver update is needed.
Signed-off-by: Masaharu Hayakawa <masaharu.hayakawa.ry@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/devicetree/bindings/watchdog/renesas-wdt.txt

@@ -16,6 +16,7 @@ Required properties:
 	         - "renesas,r8a7796-wdt" (R-Car M3-W)
 		 - "renesas,r8a77965-wdt" (R-Car M3-N)
 	         - "renesas,r8a77970-wdt" (R-Car V3M)
+	         - "renesas,r8a77990-wdt" (R-Car E3)
 	         - "renesas,r8a77995-wdt" (R-Car D3)
 	         - "renesas,r7s72100-wdt" (RZ/A1)
 		The generic compatible string must be: