iu_client: allow to control the notifications

The iu_client is informing the library user about global event.
In prepration to the tx_iu_release_free() call allow to
disable upstream notificatiosn

Change-Id: Ic93ef6fd54c995405e9c37a5e0c53f81a89850b7
diff --git a/include/osmocom/ranap/iu_client.h b/include/osmocom/ranap/iu_client.h
index 0cb84da..b388529 100644
--- a/include/osmocom/ranap/iu_client.h
+++ b/include/osmocom/ranap/iu_client.h
@@ -30,6 +30,7 @@
 	int integrity_active;
 	struct gprs_ra_id ra_id;
 	enum ranap_nsap_addr_enc rab_assign_addr_enc;
+	bool notification; /* send notification to the upstream user */
 };
 
 enum ranap_iu_event_type {