bsc: Readd the core network code setting

This will instruct the BSC to patch messages and replace
the old network code with the new one.
diff --git a/openbsc/include/openbsc/osmo_msc_data.h b/openbsc/include/openbsc/osmo_msc_data.h
index 4205c15..c058a0a 100644
--- a/openbsc/include/openbsc/osmo_msc_data.h
+++ b/openbsc/include/openbsc/osmo_msc_data.h
@@ -41,6 +41,7 @@
 	struct timer_list ping_timer;
 	struct timer_list pong_timer;
 	struct bsc_msc_connection *msc_con;
+	int core_ncc;
 
 	/* mgcp agent */
 	struct write_queue mgcp_agent;