Only sysmobts-v2 will override it, but all other machines should have
the same configuration as the sysmocom-bsc. This will fix the build of
our yocto-dora for sysmocom-idu/sysmocom-odu, where task-sysmocom-feed
pulls in task-gprscore which in turn wants to build the ggsn
configuration even on those machines where we don't actually have a ggsn
so far.
