Simulator: Add performance counter for incoming packet interval

src/modules/simulator/simulator_mavlink.cpp

@@ -248,6 +248,7 @@ void Simulator::handle_message(mavlink_message_t *msg, bool publish)
 			uint64_t timestamp = ts.tv_sec * 1000 * 1000 + ts.tv_nsec / 1000;
 
 			perf_set(_perf_sim_delay, timestamp - sim_timestamp);
+			perf_count(_perf_sim_interval);
 
 			if (publish) {
 				publish_sensor_topics(&imu);