mlxsw: spectrum_router: Start using new trap adjacency entry

Start using the trap adjacency entry that was added in the previous
patch and remove the existing one which is no longer needed.

Note that the name of the old entry was inaccurate as the entry did not
discard packets, but trapped them.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>