net/mlx5e: Add hairpin params structure

In preparation for downstream work to expose hairpin queues parameters,
introduce a hairpin parameters struct as part of the tc structure.

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