[signal] Differentiate paging success from expiration in SS_PAGING

This is useful information to know and actually fixes a segfault
in rllp.c where lchan is accessed even tough it could be NULL in
case of failure.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/gsm_04_08_utils.c b/openbsc/src/gsm_04_08_utils.c
index a184277..d5785f9 100644
--- a/openbsc/src/gsm_04_08_utils.c
+++ b/openbsc/src/gsm_04_08_utils.c
@@ -490,7 +490,7 @@
 
 	bts->network->stats.paging.completed++;
 
-	dispatch_signal(SS_PAGING, S_PAGING_COMPLETED, &sig_data);
+	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);