net/mlx4_core: Call synchronize_irq() before freeing EQ buffer

After moving the EQ ownership to software effectively destroying it, call
synchronize_irq() to ensure that any handler routines running on other CPU
cores finish execution. Only then free the EQ buffer.
The same thing is done when we destroy a CQ which is one of the sources
generating interrupts. In the case of CQ we want to avoid completion handlers
on a CQ that was destroyed. In the case we do the same to avoid receiving
asynchronous events after the EQ has been destroyed and its buffers freed.
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/eq.c

@@ -1026,6 +1026,7 @@ static void mlx4_free_eq(struct mlx4_dev *dev,
 				pr_cont("\n");
 		}
 	}
+	synchronize_irq(eq->irq);
 
 	mlx4_mtt_cleanup(dev, &eq->mtt);
 	for (i = 0; i < npages; ++i)