bsc_api: Make paging/silent call work with the subscriber_connection

Do not use the lchan for the paging but operate on the
subscriber_connection, change the signals too to not carry
the lchan but the subscriber connection... the silent call
and vty code still assume there is a lchan inside the
subscriber connection.
diff --git a/openbsc/src/gsm_04_08_utils.c b/openbsc/src/gsm_04_08_utils.c
index 952d724..3776565 100644
--- a/openbsc/src/gsm_04_08_utils.c
+++ b/openbsc/src/gsm_04_08_utils.c
@@ -268,14 +268,14 @@
 
 	sig_data.subscr = subscr;
 	sig_data.bts	= msg->lchan->ts->trx->bts;
-	sig_data.lchan	= msg->lchan;
+	sig_data.conn	= &msg->lchan->conn;
 
 	counter_inc(bts->network->stats.paging.completed);
 
 	dispatch_signal(SS_PAGING, S_PAGING_SUCCEEDED, &sig_data);
 
 	/* Stop paging on the bts we received the paging response */
-	paging_request_stop(msg->trx->bts, subscr, msg->lchan);
+	paging_request_stop(msg->trx->bts, subscr, &msg->lchan->conn);
 	return 0;
 }