vty: Change the return type from enum to int

clang complained that different enums are mixed with the
return type and we actually want this to be an int now.
diff --git a/openbsc/src/gprs/gb_proxy_main.c b/openbsc/src/gprs/gb_proxy_main.c
index 3da0abe..45b45a4 100644
--- a/openbsc/src/gprs/gb_proxy_main.c
+++ b/openbsc/src/gprs/gb_proxy_main.c
@@ -189,7 +189,7 @@
 
 extern void *tall_msgb_ctx;
 
-extern enum node_type bsc_vty_go_parent(struct vty *vty);
+extern int bsc_vty_go_parent(struct vty *vty);
 
 static struct vty_app_info vty_info = {
 	.name 		= "OsmoGbProxy",