osmo-hnbgw: don't configure specific local IP address for STP connection

It's not necessary to set a local IP to connect to OsmoSTP with, 'any' is as
good as any.

Related: OS#2663
Change-Id: If5d0a1500de5e2c4b80acf025761d0264a8a51a0
diff --git a/src/hnbgw.c b/src/hnbgw.c
index 5c0570e..c1b931c 100644
--- a/src/hnbgw.c
+++ b/src/hnbgw.c
@@ -478,8 +478,7 @@
 
 	ranap_set_log_area(DRANAP);
 
-	rc = hnbgw_cnlink_init(g_hnb_gw,
-			       "127.0.0.1", M3UA_PORT, "127.0.0.5" /* FIXME: configurable */);
+	rc = hnbgw_cnlink_init(g_hnb_gw, "127.0.0.1", M3UA_PORT, NULL);
 	if (rc < 0) {
 		LOGP(DMAIN, LOGL_ERROR, "Failed to initialize SCCP link to CN\n");
 		exit(1);