mavlink: use new copy_if_updated interface

src/modules/mavlink/mavlink_main.cpp

@@ -1812,7 +1812,6 @@ Mavlink::task_main(int argc, char *argv[])
 	MavlinkOrbSubscription *ack_sub = add_orb_subscription(ORB_ID(vehicle_command_ack));
 	uint64_t ack_time = 0;
 	MavlinkOrbSubscription *mavlink_log_sub = add_orb_subscription(ORB_ID(mavlink_log));
-	uint64_t mavlink_log_time = 0;
 
 	struct vehicle_status_s status;
 	status_sub->update(&status_time, &status);
@@ -2069,7 +2068,7 @@ Mavlink::task_main(int argc, char *argv[])
 		}
 
 		struct mavlink_log_s mavlink_log;
-		if (mavlink_log_sub->update(&mavlink_log_time, &mavlink_log)) {
+		if (mavlink_log_sub->update_if_changed(&mavlink_log)) {
 			_logbuffer.put(&mavlink_log);
 		}