bsc: Make bsc_queue_for_msc work on the osmo_bsc_sccp_con

The gsm_subscriber_connection can die before the SCCP connection
so we should work on the osmo_bsc_sccp_con.
diff --git a/openbsc/include/openbsc/osmo_bsc.h b/openbsc/include/openbsc/osmo_bsc.h
index b94fc04..01509c0 100644
--- a/openbsc/include/openbsc/osmo_bsc.h
+++ b/openbsc/include/openbsc/osmo_bsc.h
@@ -22,7 +22,7 @@
 
 struct bsc_api *osmo_bsc_api();
 
-int bsc_queue_for_msc(struct gsm_subscriber_connection *conn, struct msgb *msg);
+int bsc_queue_for_msc(struct osmo_bsc_sccp_con *conn, struct msgb *msg);
 int bsc_open_connection(struct osmo_bsc_sccp_con *sccp, struct msgb *msg);
 int bsc_create_new_connection(struct gsm_subscriber_connection *conn);
 int bsc_delete_connection(struct osmo_bsc_sccp_con *sccp);