[Cake] cake breaks on net-next head

[Dave Täht]

As I have accumulated enough hardware to do some basic cake testing
again, I spent a bit of time trying to get it to build, and did not
succeed.

There has been some activity in the world (discussed at the netconf
conference - I was not there so I lack details) about modifying how
ingress works, so I assume it has something to do with that (AT_INGRESS
and G_TC_AT are undefined).

patches gladly accepted.