sgsn: migrate to the new gprs_ns2_vty configuration

Change the whole vty configuration for NS to be more flexible
and support more setups. Old configurations are invalid.

API change which must be synchronized with libosmocore

For further information see:
https://osmocom.org/projects/libosmocore/wiki/Network_service_(NS)

Depends-on: I8c3f2afecc74b78f7f914f7dce166cbcb63444eb (libosmocore)
Change-Id: Ie9306ab4d4738c2c57a69987086e22771b30657e
diff --git a/src/sgsn/sgsn_main.c b/src/sgsn/sgsn_main.c
index 19039f6..f6eac60 100644
--- a/src/sgsn/sgsn_main.c
+++ b/src/sgsn/sgsn_main.c
@@ -328,11 +328,6 @@
 int main(int argc, char **argv)
 {
 	int rc;
-	struct osmo_sockaddr_str bind_address = {
-		.af = AF_INET,
-		.ip = "0.0.0.0",
-		.port = 23000,
-	};
 #if BUILD_IU
 	struct osmo_sccp_instance *sccp;
 #endif
@@ -402,7 +397,7 @@
 	sgsn_inst_init(sgsn);
 
 
-	gprs_ns2_vty_init(sgsn_nsi, &bind_address);
+	gprs_ns2_vty_init(sgsn_nsi);
 	bssgp_vty_init();
 	gprs_llc_vty_init();
 	gprs_sndcp_vty_init();
@@ -449,12 +444,6 @@
 		exit(2);
 	}
 
-	rc = gprs_ns2_vty_create();
-	if (rc < 0) {
-		LOGP(DGPRS, LOGL_FATAL, "Cannot bind/listen on NSIP socket\n");
-		exit(2);
-	}
-
 	gprs_ns2_dynamic_create_nse(sgsn_nsi, true);
 
 	if (sgsn->cfg.dynamic_lookup) {