gbproxy: Use "(nsei << 16) | bvci" as rate_ctr_group index

As we now have gbproxy_bvc on both the SGSN and the BSS side
with the same BVCI, using the BVCI alone will no longer render
unique indexes.

Related: OS#4472
Change-Id: I13f3c9e69562a56ad7d3742fdeb2ba48f134fdaa
diff --git a/src/gb_proxy_peer.c b/src/gb_proxy_peer.c
index a0586fe..ed7df32 100644
--- a/src/gb_proxy_peer.c
+++ b/src/gb_proxy_peer.c
@@ -77,7 +77,7 @@
 		return NULL;
 
 	bvc->bvci = bvci;
-	bvc->ctrg = rate_ctr_group_alloc(bvc, &bvc_ctrg_desc, bvci);
+	bvc->ctrg = rate_ctr_group_alloc(bvc, &bvc_ctrg_desc, (nse->nsei << 16) | bvci);
 	if (!bvc->ctrg) {
 		talloc_free(bvc);
 		return NULL;