add mgcp_conn_rtp_type_names[]

First use in upcoming Ib89a6779e1d68c6600f00699d4303f6c0ee07132

Change-Id: If3d8bc68a3b26d3aa0ba7eedeab67b820889ed54
diff --git a/src/libosmo-mgcp/mgcp_conn.c b/src/libosmo-mgcp/mgcp_conn.c
index 0ba10e5..afc9e4e 100644
--- a/src/libosmo-mgcp/mgcp_conn.c
+++ b/src/libosmo-mgcp/mgcp_conn.c
@@ -441,3 +441,10 @@
 
 	return llist_last_entry(&endp->conns, struct mgcp_conn, entry);
 }
+
+const struct value_string mgcp_conn_rtp_type_names[] = {
+	{ MGCP_RTP_DEFAULT, "rtp" },
+	{ MGCP_RTP_OSMUX, "osmux" },
+	{ MGCP_RTP_IUUP, "iuup" },
+	{}
+};