bssgp: Introduce "GLOBAL" port for PTP BVC

There are some messages/procedures on a PTP BVC which are not related
to one specific TLLI, but affect the whole PTP BVC.  First and foremost
that is the FLOW-CONTROL-BVC. Let's check if the user is interested in
handling those internally (by connecting to the GLOBAL port).  If not,
fall back to acknowledging all incoing FC-BVC and ignoring all ACKs.

Related: OS#4891
Change-Id: Ib80a6a522dbcb33fd0e7bd31a73ef28fdc636f57
1 file changed