osmo_msc: remove unused parameter from msc_dtap()

The parameter link_id in the function msc_dtap() is unused. Lets remove
it.

Change-Id: I7ba67b0cb514c91bc87a7b396ed3962b7a68e7da
diff --git a/src/libmsc/osmo_msc.c b/src/libmsc/osmo_msc.c
index c9ecb64..f2c84e6 100644
--- a/src/libmsc/osmo_msc.c
+++ b/src/libmsc/osmo_msc.c
@@ -121,7 +121,7 @@
 }
 
 /* Receive a DTAP message from BSC */
-void msc_dtap(struct gsm_subscriber_connection *conn, uint8_t link_id, struct msgb *msg)
+void msc_dtap(struct gsm_subscriber_connection *conn, struct msgb *msg)
 {
 	msc_subscr_conn_get(conn, MSC_CONN_USE_DTAP);
 	gsm0408_dispatch(conn, msg);