sgsn: Fix regression regarding g_pars.bssgp.cell_id[] array overflow

This was introduced in I7d859fd710dba96eb9b46c428243281183e1be12
and caused Iu related TTCN3 tests to fail with:

SGSN_Tests.ttcn:771 Dynamic test case error: Index overflow in a value of type @SGSN_Tests.BssgpCellIds: The index is 3, but the value has only 3 elements.

Change-Id: Iaae0015f5e7c7eabc426add91b5de1b63bf6d9f6
1 file changed