watchdog: Add Renesas RZ/N1 Watchdog driver

This is a driver for the standard WDT on the RZ/N1 devices. This WDT has
very limited timeout capabilities. However, it can reset the device.
To do so, the corresponding bits in the SysCtrl RSTEN register need to
be enabled. This is not done by this driver.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220427135531.708279-3-jjhiblot@traphandler.com


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