imx_watchdog: always set minimal timeout in reset_cpu

The problem is that timeout bits in WCR register were leaved unchanged.
So previously set timeout value was applied and therefore 'reset'
command takes any value up to two minutes, depending on previous
watchdog settings, instead of minimal 0.5 seconds.

Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>

drivers/watchdog/imx_watchdog.c

@@ -43,7 +43,7 @@ void reset_cpu(ulong addr)
 {
 	struct watchdog_regs *wdog = (struct watchdog_regs *)WDOG1_BASE_ADDR;
 
-	clrsetbits_le16(&wdog->wcr, 0, WCR_WDE);
+	clrsetbits_le16(&wdog->wcr, WCR_WT_MSK, WCR_WDE);
 
 	writew(0x5555, &wdog->wsr);
 	writew(0xaaaa, &wdog->wsr);	/* load minimum 1/2 second timeout */

include/fsl_wdog.h

@@ -16,3 +16,4 @@ struct watchdog_regs {
 #define WCR_WDT		0x08
 #define WCR_SRS		0x10
 #define SET_WCR_WT(x)	(x << 8)
+#define WCR_WT_MSK	SET_WCR_WT(0xFF)