watchdog: f71808e_wdt: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Notice that in this particular case I replaced "Fall" with a proper
"fall through" comment, which is what GCC is expecting to find.
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/f71808e_wdt.c

@@ -627,7 +627,7 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 
 		if (new_options & WDIOS_ENABLECARD)
 			return watchdog_start();
-
+		/* fall through */
 
 	case WDIOC_KEEPALIVE:
 		watchdog_keepalive();
@@ -641,7 +641,7 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 			return -EINVAL;
 
 		watchdog_keepalive();
-		/* Fall */
+		/* fall through */
 
 	case WDIOC_GETTIMEOUT:
 		return put_user(watchdog.timeout, uarg.i);