This is the OsmoBSC project. Disabling the build of the BSC would be
somewhat odd, so let's remove the option.
Also, OsmoBSC depends on libosmo-sccp now, so we must unconditionally
depend on it. As a result, we can remove the --enable-nat option,
as this was only to avoid a mandatory libosmo-sccp requirement in
historical times.
Change-Id: Icfee8a904d33b7c13ab8d185d64fb5c2337d8640