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

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

Driver shouldn't allow to use UMR to register a MR when
umr_modify_atomic_disabled is set. Otherwise it will always end up with a
failure in the post send flow which sets the UMR WQE to modify atomic access
right.

Fixes: c8d75a980fab ("IB/mlx5: Respect new UMR capabilities")
Signed-off-by: Guy Levi <guyle@mellanox.com>
Reviewed-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Link: https://lore.kernel.org/r/20190731081929.32559-1-leon@kernel.org
Signed-off-by: Doug Ledford <dledford@redhat.com>