net/mlx5: DR, Add support for force-loopback QP

When supported by the device, SW steering RoCE RC QP that is used to
write/read to/from ICM will be created with force-loopback attribute.
Such QP doesn't require GID index upon creation.

Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>