documentation: watchdog: add documentation for armada-37xx-wdt

Add documentation for the kernel module parameters accepted by
armada-37xx-wdt.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/watchdog/watchdog-parameters.txt

@@ -40,6 +40,11 @@ margin: Watchdog margin in seconds (default=60)
 nowayout: Disable watchdog shutdown on close
 	(default=kernel config parameter)
 -------------------------------------------------
+armada_37xx_wdt:
+timeout: Watchdog timeout in seconds. (default=120)
+nowayout: Disable watchdog shutdown on close
+	(default=kernel config parameter)
+-------------------------------------------------
 at91rm9200_wdt:
 wdt_time: Watchdog time in seconds. (default=5)
 nowayout: Watchdog cannot be stopped once started