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/include/fsl_wdog.h b/include/fsl_wdog.h
index f698d4d..683c3f3 100644
--- a/include/fsl_wdog.h
+++ b/include/fsl_wdog.h
@@ -15,5 +15,6 @@
 #define WCR_WDE		0x04
 #define WCR_WDT		0x08
 #define WCR_SRS		0x10
+#define WCR_WDA 	0x20
 #define SET_WCR_WT(x)	(x << 8)
 #define WCR_WT_MSK	SET_WCR_WT(0xFF)