imx_watchdog: Do not assert WDOG_B on watchdog init

Currently the driver asserts WDOG_B by clearing WCR_WDA bit when
enabling the watchdog. Do not clear WCR_WDA.

Signed-off-by: Ross Parker <rossjparker@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/drivers/watchdog/imx_watchdog.c b/drivers/watchdog/imx_watchdog.c
index 2938d9f..3f826d1 100644
--- a/drivers/watchdog/imx_watchdog.c
+++ b/drivers/watchdog/imx_watchdog.c
@@ -34,7 +34,7 @@
 #endif
 	timeout = (CONFIG_WATCHDOG_TIMEOUT_MSECS / 500) - 1;
 	writew(WCR_WDZST | WCR_WDBG | WCR_WDE | WCR_WDT | WCR_SRS |
-		SET_WCR_WT(timeout), &wdog->wcr);
+		WCR_WDA | SET_WCR_WT(timeout), &wdog->wcr);
 	hw_watchdog_reset();
 }
 #endif