dt-bindings: watchdog: renesas,wdt: Add support for RZ/N1

Describe the WDT hardware in the RZ/N1 series.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220427135531.708279-2-jjhiblot@traphandler.com


[groeck: Rebased, fixed conflicts]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>