net/mlx5: implement drop action in hardware classifier

net/mlx5: implement drop action in hardware classifier

The current drop action is implemented as a queue tail drop,
requiring to instantiate multiple WQs to maintain high drop rate.
This commit, implements the drop action in hardware classifier.
This enables to reduce the amount of contexts needed for the drop,
without affecting the drop rate.

Signed-off-by: Shachar Beiser <shacharbe@mellanox.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>