fix some more compiler warnings

diff --git a/include/openbsc/telnet_interface.h b/include/openbsc/telnet_interface.h
index b5a0ec4..97357d7 100644
--- a/include/openbsc/telnet_interface.h
+++ b/include/openbsc/telnet_interface.h
@@ -47,4 +47,6 @@
 
 void telnet_init(struct gsm_network *network, int port);
 
+int bsc_vty_init(struct gsm_network *net);
+
 #endif