[WATCHDOG] machzwd warning fix

From: Andrew Morton <akpm@linux-foundation.org>

drivers/char/watchdog/machzwd.c: In function 'zf_ioctl':
drivers/char/watchdog/machzwd.c:327: warning: passing argument 1 of 'zf_ping' makes integer from pointer without a cast
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/char/watchdog/machzwd.c

@@ -324,7 +324,7 @@ static int zf_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
 			return put_user(0, p);
 
 		case WDIOC_KEEPALIVE:
-			zf_ping(NULL);
+			zf_ping(0);
 			break;
 
 		default: