net/mlx5: Avoid double free in fs init error unwinding path

In below code flow, for ingress acl table root ns memory leads
to double free.

mlx5_init_fs
  init_ingress_acls_root_ns()
    init_ingress_acl_root_ns
       kfree(steering->esw_ingress_root_ns);
       /* steering->esw_ingress_root_ns is not marked NULL */
  mlx5_cleanup_fs
    cleanup_ingress_acls_root_ns
       steering->esw_ingress_root_ns non NULL check passes.
       kfree(steering->esw_ingress_root_ns);
       /* double free */

Similar issue exist for other tables.

Hence zero out the pointers to not process the table again.

Fixes: 9b93ab98

 ("net/mlx5: Separate ingress/egress namespaces for each vport")
Fixes: 40c3eebb49e51 ("net/mlx5: Add support in RDMA RX steering")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>