net/mlx5: Move TISes from priv to mdev HW resources

The transport interface send (TIS) object is responsible for performing
all transport related operations of the transmit side. Messages from
Send Queues get segmented and transmitted by the TIS including all
transport required implications, e.g. in the case of large send offload,
the TIS is responsible for the segmentation.

These are stateless objects and can be used by multiple netdevs (e.g.
representors) who share the same core device.

Providing the TISes as a service from the core layer to the netdev layer
reduces the number of replecated TIS objects (in case of multiple
netdevs), and will ease the transition to netdev with multiple mdevs.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>