watchdog: docs: add an entry for imx2_wdt

Add an entry for imx2_wdt in watchdog-parameters.txt
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

Documentation/watchdog/watchdog-parameters.txt

@@ -125,6 +125,11 @@ ibmasr:
 nowayout: Watchdog cannot be stopped once started
 	(default=kernel config parameter)
 -------------------------------------------------
+imx2_wdt:
+timeout: Watchdog timeout in seconds (default 60 s)
+nowayout: Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+-------------------------------------------------
 indydog:
 nowayout: Watchdog cannot be stopped once started
 	(default=kernel config parameter)