imx: wdog: correct wcr register settings

We should not simple use "writew(WCR_WDE, &wdog->wcr)" to set
wcr, since this will override bits set before reset_cpu.

Use clrsetbits_le16 instead of writew to fix this issue.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>

drivers/watchdog/imx_watchdog.c

@@ -55,7 +55,8 @@ void reset_cpu(ulong addr)
 {
 	struct watchdog_regs *wdog = (struct watchdog_regs *)WDOG1_BASE_ADDR;
 
-	writew(WCR_WDE, &wdog->wcr);
+	clrsetbits_le16(&wdog->wcr, 0, WCR_WDE);
+
 	writew(0x5555, &wdog->wsr);
 	writew(0xaaaa, &wdog->wsr);	/* load minimum 1/2 second timeout */
 	while (1) {