Use port number #defines for VTY and CTRL ports

.. as defined in libosmocore
diff --git a/openbsc/src/libbsc/bsc_init.c b/openbsc/src/libbsc/bsc_init.c
index 8fd72cf..796d027 100644
--- a/openbsc/src/libbsc/bsc_init.c
+++ b/openbsc/src/libbsc/bsc_init.c
@@ -27,6 +27,7 @@
 #include <openbsc/debug.h>
 #include <openbsc/misdn.h>
 #include <osmocom/vty/telnet_interface.h>
+#include <osmocom/vty/ports.h>
 #include <openbsc/system_information.h>
 #include <openbsc/paging.h>
 #include <openbsc/signal.h>
@@ -478,7 +479,7 @@
 		return rc;
 	}
 
-	rc = telnet_init(tall_bsc_ctx, bsc_gsmnet, 4242);
+	rc = telnet_init(tall_bsc_ctx, bsc_gsmnet, OSMO_VTY_PORT_NITB_BSC);
 	if (rc < 0)
 		return rc;