AP_MotorsHeli_Single: use RSC class's get_idle_output function

No functional change

libraries/AP_Motors/AP_MotorsHeli_Single.cpp

@@ -382,7 +382,7 @@ void AP_MotorsHeli_Single::move_actuators(float roll_out, float pitch_out, float
         // rudder feed forward based on collective
         // the feed-forward is not required when the motor is stopped or at idle, and thus not creating torque
         // also not required if we are using external gyro
-        if ((_main_rotor.get_control_output() > _rsc_idle_output) && _tail_type != AP_MOTORS_HELI_SINGLE_TAILTYPE_SERVO_EXTGYRO) {
+        if ((_main_rotor.get_control_output() > _main_rotor.get_idle_output()) && _tail_type != AP_MOTORS_HELI_SINGLE_TAILTYPE_SERVO_EXTGYRO) {
             // sanity check collective_yaw_effect
             _collective_yaw_effect = constrain_float(_collective_yaw_effect, -AP_MOTORS_HELI_SINGLE_COLYAW_RANGE, AP_MOTORS_HELI_SINGLE_COLYAW_RANGE);
             yaw_offset = _collective_yaw_effect * fabsf(collective_out - (_collective_mid_pwm/1000.0f));