auth: Fix AuthTupe re-use condition

It's not the key_seq of the last authtuple we must check, but
the one sent by the MS.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

openbsc/src/auth.c

@@ -87,7 +87,7 @@ int auth_get_tuple_for_subscr(struct gsm_auth_tuple *atuple,
 	/* If possible, re-use the last tuple and skip auth */
 	rc = db_get_lastauthtuple_for_subscr(atuple, subscr);
 	if ((rc == 0) &&
-	    (atuple->key_seq != GSM_KEY_SEQ_INVAL) &&
+	    (key_seq != GSM_KEY_SEQ_INVAL) &&
 	    (atuple->use_count < 3))
 	{
 		atuple->use_count++;