[CONNECTOR]: Fix warning in cn_queue.c

cn_queue.c:130: warning: value computed is not used

There is no point in testing the atomic value if the result is thrown
away.

From Evgeniy:

It was created to put implicit smp barrier, but it is not needed there.
Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/connector/cn_queue.c

@@ -127,7 +127,7 @@ void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id)
 
 	if (found) {
 		cn_queue_free_callback(cbq);
-		atomic_dec_and_test(&dev->refcnt);
+		atomic_dec(&dev->refcnt);
 	}
 }