IB/mlx4: Fix possible missed completion event

If an erroneous CQE is polled in the first iteration (i.e. npolled ==
0), we don't update the consumer index and hence the hardware could
get a wrong notion of how many CQEs software polled.  Fix this by
unconditionally updating the doorbell record.  We could change the
check to be something like

	if (npolled || err != -EAGAIN)
		...

but it does not seem worth the effort since a posted write to memory
should not cost too much.
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx4/cq.c

@@ -747,8 +747,7 @@ int mlx4_ib_poll_cq(struct ib_cq *ibcq, int num_entries, struct ib_wc *wc)
 			break;
 	}
 
-	if (npolled)
-		mlx4_cq_set_ci(&cq->mcq);
+	mlx4_cq_set_ci(&cq->mcq);
 
 	spin_unlock_irqrestore(&cq->lock, flags);