dt-bindings: watchdog: renesas-wdt: Add support for R-Car V4M

Add documentation for r8a779h0 compatible string to
Renesas watchdog device tree bindings documentation.

Signed-off-by: Minh Le <minh.le.aj@renesas.com>
Signed-off-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/8c2eaad577513a519c518698a45083afb65b16f0.1706789940.git.geert+renesas@glider.be


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>