net/mlx5e: HTB, remove priv from htb function calls

As a step to make htb self-contained replace the passing of priv as a
parameter to htb function calls with members in the htb struct.

Full decoupling the htb from priv will require more work, so for now
leave the priv as one of the members in the htb struct, to be replaced
by channels in a future commit.

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