mme: Use LAC from SGSN with most significat bit set to 0

According to 3GPP TS 23.003 sec 2.8.2.2.2, LACs from GERAN are
configured with MSB 0 in order to differentiate it from EUTRAN ones.
This is used by MMEs to figure out if the peer is an SGSN, based on
the the LAC mapped into MME group ID in GUTI .

Change-Id: Iaf89228f6f026e04d5f583211959025e6d8d4a1d
1 file changed