modules/sca: restore missing prototype.

sca_subscription_aor_has_subscribers
(cherry picked from commit 7bf7e9f858faab2329e5edf3d988bef76ac2c804)

modules/sca/sca_subscribe.h

@@ -88,6 +88,7 @@ void	sca_subscription_db_update_timer( unsigned, void * );
 void	sca_subscription_purge_expired( unsigned int, void * );
 void	sca_subscription_state_to_str( int, str * );
 
+int	sca_subscription_aor_has_subscribers( int, str * );
 int	sca_subscription_delete_subscriber_for_event( sca_mod *, str *, str *,
 						      str * );
 int	sca_subscription_terminate( sca_mod *, str *, int, str *, int, int );