libmgcp: add enum mgcp_role

This enum indicates if the mgcp is running on the BSC or the BSC-NAT.
diff --git a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
index 540f760..596ea8a 100644
--- a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
+++ b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
@@ -223,7 +223,7 @@
 
 	handle_options(argc, argv);
 
-        rc = mgcp_parse_config(config_file, cfg);
+	rc = mgcp_parse_config(config_file, cfg, MGCP_BSC);
 	if (rc < 0)
 		return rc;