wdt: nuvoton: Fix reset/expire function error

Fix npcm845 watchdog halt for reset function and expire function.
Reset function is restart wdt.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/watchdog/npcm_wdt.c b/drivers/watchdog/npcm_wdt.c
index e56aa0e..57b6121 100644
--- a/drivers/watchdog/npcm_wdt.c
+++ b/drivers/watchdog/npcm_wdt.c
@@ -69,15 +69,21 @@
 static int npcm_wdt_reset(struct udevice *dev)
 {
 	struct npcm_wdt_priv *priv = dev_get_priv(dev);
+	u32 val;
 
-	writel(NPCM_WTR | NPCM_WTRE | NPCM_WTE, priv->regs);
+	val = readl(priv->regs);
+	writel(val | NPCM_WTR, priv->regs);
 
 	return 0;
 }
 
 static int npcm_wdt_expire_now(struct udevice *dev, ulong flags)
 {
-	return npcm_wdt_reset(dev);
+	struct npcm_wdt_priv *priv = dev_get_priv(dev);
+
+	writel(NPCM_WTR | NPCM_WTRE | NPCM_WTE, priv->regs);
+
+	return 0;
 }
 
 static int npcm_wdt_of_to_plat(struct udevice *dev)