This adds support for using the "template add" and "template destroy"
functionality to change the port keyset configuration.

If the VCAP lookup already contains rules, the port keyset is left
unchanged, as a change would make these rules unusable.

When the template is destroyed the port keyset configuration is restored.
The filters using the template chain will automatically be deleted by the
TC framework.
Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>