IB/mlx5: Fix MR re-registration flow to use UMR properly

The UMR WQE in the MR re-registration flow requires that
modify_atomic and modify_entity_size capabilities are enabled.
Therefore, check that the these capabilities are present before going to
umr flow and go through slow path if not.

Fixes: c8d75a98

 ("IB/mlx5: Respect new UMR capabilities")
Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Guy Levi <guyle@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Link: https://lore.kernel.org/r/20190815083834.9245-8-leon@kernel.org
Signed-off-by: Doug Ledford <dledford@redhat.com>