net/mlx4_core: Fix mailbox leak in error flow when performing update qp

The procedure mlx4_update_qp leaks mailboxes in its error-flow, fix that.
Signed-off-by: NJack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -422,15 +422,15 @@ int mlx4_update_qp(struct mlx4_dev *dev, u32 qpn,
 	u64 qp_mask = 0;
 	int err = 0;
 
+	if (!attr || (attr & ~MLX4_UPDATE_QP_SUPPORTED_ATTRS))
+		return -EINVAL;
+
 	mailbox = mlx4_alloc_cmd_mailbox(dev);
 	if (IS_ERR(mailbox))
 		return PTR_ERR(mailbox);
 
 	cmd = (struct mlx4_update_qp_context *)mailbox->buf;
 
-	if (!attr || (attr & ~MLX4_UPDATE_QP_SUPPORTED_ATTRS))
-		return -EINVAL;
-
 	if (attr & MLX4_UPDATE_QP_SMAC) {
 		pri_addr_path_mask |= 1ULL << MLX4_UPD_QP_PATH_MASK_MAC_INDEX;
 		cmd->qp_context.pri_path.grh_mylmc = params->smac_index;