RDMA/core: Require the driver to set the IOVA correctly during rereg_mr

RDMA/core: Require the driver to set the IOVA correctly during rereg_mr

If the driver returns a new MR during rereg it has to fill it with the
IOVA from the proper source. If IB_MR_REREG_TRANS is set then the IOVA is
cmd.hca_va, otherwise the IOVA comes from the old MR. mlx5 for example has
two calls inside rereg_mr:

		return create_real_mr(new_pd, umem, mr->ibmr.iova,
				      new_access_flags);
and
		return create_real_mr(new_pd, new_umem, iova, new_access_flags);

Unconditionally overwriting the iova in the newly allocated MR will
corrupt the iova if the first path is used.

Remove the redundant initializations from ib_uverbs_rereg_mr().

Fixes: a16f35bba5fe ("RDMA/uverbs: Allow drivers to create a new HW object during rereg_mr")
Link: https://lore.kernel.org/r/4b0a31bbc372842613286a10d7a8cbb0ee6069c7.1635400472.git.leonro@nvidia.com
Signed-off-by: Aharon Landau <aharonl@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>