IB/mlx5: Add tx_affinity support for DCI QP

DCI QP supports tx_affinity as well.

Link: https://lore.kernel.org/r/20200818115245.700581-2-leon@kernel.org


Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>