silent_call: remove unfinished fuzzer interface

Remove the fuzzer interface that was partially implemented in
gsm_04_08.c and silent_call.c is causing problems when an
SMS is sent during an active silent call. The reason for this
is that gsm0408_dispatch() in gsm_04_08.c would decide to
rout all uplink traffic to silent_call_rx() in silent_call.c.
silent_call_rx() is a stub function that discards the data.

This patch removes the fuzzer interface code by placing ifdefs
around it, so that it can be re-activated by experimentators.

Change-Id: Id500197d58663b3f4b1756136343670388b0a4bc
diff --git a/openbsc/include/openbsc/silent_call.h b/openbsc/include/openbsc/silent_call.h
index 2492903..619a543 100644
--- a/openbsc/include/openbsc/silent_call.h
+++ b/openbsc/include/openbsc/silent_call.h
@@ -6,7 +6,10 @@
 extern int gsm_silent_call_start(struct gsm_subscriber *subscr,
                                  void *data, int type);
 extern int gsm_silent_call_stop(struct gsm_subscriber *subscr);
+
+#if 0
 extern int silent_call_rx(struct gsm_subscriber_connection *conn, struct msgb *msg);
 extern int silent_call_reroute(struct gsm_subscriber_connection *conn, struct msgb *msg);
+#endif
 
 #endif /* _SILENT_CALL_H */