net/mlx5e: HTB, move ids to selq_params struct

HTB id fields are needed for selecting queue. Moving them to the
selq_params struct will simplify synchronization between control flow
and mlx5e_select_queues and will keep the IDs in the hot cacheline of
mlx5e_selq_params.

Replace mlx5e_selq_prepare() with separate functions that change subsets
of parameters, while keeping the rest.

This also will be useful to hide mlx5e_htb structure from the rest of the
driver in a later patch in this series.

Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Moshe Tal <moshet@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@nvidia.com>