dt-bindings: watchdog: renesas-wdt: Add support for the r8a77970 wdt

Document support for the Watchdog Timer (WDT) Controller in the Renesas
R-Car V3M (r8a77970) SoC.  Restore sort order while at it.

No driver update is needed.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>