EKF: Use estimator scheduling order

src/modules/ekf2/ekf2_main.cpp

@@ -1515,7 +1515,7 @@ int Ekf2::task_spawn(int argc, char *argv[])
 {
 	_task_id = px4_task_spawn_cmd("ekf2",
 				      SCHED_DEFAULT,
-				      SCHED_PRIORITY_MAX - 5,
+				      SCHED_PRIORITY_ESTIMATOR,
 				      5900,
 				      (px4_main_t)&run_trampoline,
 				      (char *const *)argv);