IB/mlx4: Remove redundant NULL check before kfree

kfree on NULL pointer is a no-op.
Signed-off-by: Syam Sidhardhan <s.syam@samsung.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx4/main.c

@@ -1601,7 +1601,6 @@ static void do_slave_init(struct mlx4_ib_dev *ibdev, int slave, int do_init)
 		spin_unlock_irqrestore(&ibdev->sriov.going_down_lock, flags);
 	}
 out:
-	if (dm)
 	kfree(dm);
 	return;
 }