dt-bindings: watchdog: da9062: add watchdog timeout mode

Document the watchdog timeout mode property. If this property is used
the user can select what happens on watchdog timeout. Set this property
to 1 to enable SHUTDOWN (the device resets), set it to 0 and the device
will go to POWERDOWN on watchdog timeout.

If this property is not set, don't touch the WATCHDOG_SD bit and leave
the configuration to OTP. This way backward compatibility is not broken.

Signed-off-by: Andrej Picej <andrej.picej@norik.com>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211206064732.280375-4-andrej.picej@norik.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>