[SGSN] Fix TLLI (re)assignments

Once The TLLI (or P-TMSI of which it is derived) change has been
confirmed by the MS, we need to unassign the old TLLI but keep
the new TLLI  _without_ re-setting the LLC entity structure such
as VUsend /VUrecv counters.
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index bd5a7fa..9a43766 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -883,7 +883,7 @@
 		mmctx->p_tmsi_old = 0;
 		/* Unassign the old TLLI */
 		mmctx->tlli = mmctx->tlli_new;
-		gprs_llgmm_assign(mmctx->llme, 0xffffffff, mmctx->tlli_new, 0, NULL);
+		gprs_llgmm_assign(mmctx->llme, 0xffffffff, mmctx->tlli, 0, NULL);
 		break;
 	case GSM48_MT_GMM_RA_UPD_COMPL:
 		/* only in case SGSN offered new P-TMSI */
@@ -892,7 +892,7 @@
 		mmctx->p_tmsi_old = 0;
 		/* Unassign the old TLLI */
 		mmctx->tlli = mmctx->tlli_new;
-		gprs_llgmm_assign(mmctx->llme, 0xffffffff, mmctx->tlli_new, 0, NULL);
+		gprs_llgmm_assign(mmctx->llme, 0xffffffff, mmctx->tlli, 0, NULL);
 		break;
 	case GSM48_MT_GMM_PTMSI_REALL_COMPL:
 		DEBUGP(DMM, "-> PTMSI REALLLICATION COMPLETE\n");
@@ -900,7 +900,7 @@
 		mmctx->p_tmsi_old = 0;
 		/* Unassign the old TLLI */
 		mmctx->tlli = mmctx->tlli_new;
-		//gprs_llgmm_assign(mmctx->llme, 0xffffffff, mmctx->tlli_new, 0, NULL);
+		//gprs_llgmm_assign(mmctx->llme, 0xffffffff, mmctx->tlli, 0, NULL);
 		break;
 	case GSM48_MT_GMM_AUTH_CIPH_RESP:
 		DEBUGP(DMM, "Unimplemented GSM 04.08 GMM msg type 0x%02x\n",