libmsc: Add a function to return a unique ID of the subscriber conn

The ID will include the type of connection (GERAN_A, UTRAN_IU) followed
by the SCCP conn_id.
This can be used for the fsm instance ID before we know the IMSI.

Change-Id: I4b875772e3994ad3458ee60dbf880604486d9afd
2 files changed