IB/mlx4: Fix memory leaks

In mlx4_ib_alloc_pv_bufs(), 'tun_qp->tx_ring' is allocated through
kcalloc(). However, it is not always deallocated in the following execution
if an error occurs, leading to memory leaks. To fix this issue, free
'tun_qp->tx_ring' whenever an error occurs.
Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Link: https://lore.kernel.org/r/1566159781-4642-1-git-send-email-wenwen@cs.uga.eduSigned-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx4/mad.c

@@ -1677,8 +1677,6 @@ static int mlx4_ib_alloc_pv_bufs(struct mlx4_ib_demux_pv_ctx *ctx,
 				    tx_buf_size, DMA_TO_DEVICE);
 		kfree(tun_qp->tx_ring[i].buf.addr);
 	}
-	kfree(tun_qp->tx_ring);
-	tun_qp->tx_ring = NULL;
 	i = MLX4_NUM_TUNNEL_BUFS;
 err:
 	while (i > 0) {
@@ -1687,6 +1685,8 @@ static int mlx4_ib_alloc_pv_bufs(struct mlx4_ib_demux_pv_ctx *ctx,
 				    rx_buf_size, DMA_FROM_DEVICE);
 		kfree(tun_qp->ring[i].addr);
 	}
+	kfree(tun_qp->tx_ring);
+	tun_qp->tx_ring = NULL;
 	kfree(tun_qp->ring);
 	tun_qp->ring = NULL;
 	return -ENOMEM;