[CONNECTOR]: Return proper error code in cn_call_callback()

Error code should be set to EINVAL instead of ENODEV if !queue_work().
There's another call of queue_work() which may set err to EINVAL.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/connector/connector.c

@@ -145,6 +145,8 @@ static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), v
 				if (queue_work(dev->cbdev->cn_queue,
 							&__cbq->work))
 					err = 0;
+				else
+					err = -EINVAL;
 			} else {
 				struct cn_callback_data *d;