gtphub: add OSMO_VTY_PORT_GTPHUB.

This is for gtphub, being developed in openbsc.git.

Sponsored-by: On-Waves ehi
diff --git a/include/osmocom/vty/ports.h b/include/osmocom/vty/ports.h
index f4bc485..2d791d5 100644
--- a/include/osmocom/vty/ports.h
+++ b/include/osmocom/vty/ports.h
@@ -13,3 +13,4 @@
 #define OSMO_VTY_PORT_BB	4247
 /* 4249-4251 used by control interface */
 #define OSMO_VTY_PORT_BTSMGR	4252
+#define OSMO_VTY_PORT_GTPHUB	4253