RDMA/mlx5: Unify error flows in rereg MR failure paths

According to the IBTA spec 1.3, the driver failure in
MR reregister shall release old and new MRs.

 C11-20: If the CI returns any other error, the CI shall
 invalidate both "old" and "new" registrations, and release
 any associated resources.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>