net/mlx5e: TC, Add peer flow in mpesw mode

While at it rename mlx5_lag_mpesw_is_activated() to mlx5_lag_is_mpesw() to
be consistent with checking if other lag modes are activated.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>