mscsplit: move subscriber conns list into struct gsm_network

Replace the global sub_connections llist with gsm_network.subscr_conns.
Initialize and apply where applicable.

Remove bsc_api_sub_connections(), callers now access gsm_network->subscr_conns
directly.

This allows using the subscr_conns from libmsc without having to link libbsc.

Change-Id: Ice2a7ca04910bcfaaff22539abe68a6349e8631c
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_ctrl.c b/openbsc/src/osmo-bsc/osmo_bsc_ctrl.c
index 72f80ed..3010b55 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_ctrl.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_ctrl.c
@@ -583,7 +583,7 @@
 	alert = atoi(alert_str);
 
 	net = cmd->node;
-	llist_for_each_entry(conn, bsc_api_sub_connections(net), entry) {
+	llist_for_each_entry(conn, &net->subscr_conns, entry) {
 		if (!conn->sccp_con)
 			continue;