mc_att_control: remove useless parameter MC_YAW_FF

It scales the yawspeed setpoint arbitrarily by default with 0.5.
This makes no sense because when you give a setpoint of 1rad/s then
you expect the setpoint to get executed. If you want manual yawspeed
response to be less agressive on the stick use the scaling parameter
for the stick MPC_MAN_Y_MAX.

src/modules/mc_att_control/mc_att_control.hpp

@@ -204,8 +204,6 @@ private:
 		(ParamFloat<px4::params::MC_YAWRATE_D>) _yaw_rate_d,
 		(ParamFloat<px4::params::MC_YAWRATE_FF>) _yaw_rate_ff,
 
-		(ParamFloat<px4::params::MC_YAW_FF>) _yaw_ff,					/**< yaw control feed-forward */
-
 		(ParamFloat<px4::params::MC_DTERM_CUTOFF>) _d_term_cutoff_freq,			/**< Cutoff frequency for the D-term filter */
 
 		(ParamFloat<px4::params::MC_TPA_BREAK_P>) _tpa_breakpoint_p,			/**< Throttle PID Attenuation breakpoint */

src/modules/mc_att_control/mc_att_control_main.cpp

@@ -430,16 +430,14 @@ MulticopterAttitudeControl::control_attitude(float dt)
 	_rates_sp = eq.emult(attitude_gain);
 
 	/* Feed forward the yaw setpoint rate.
-	 * The yaw_feedforward_rate is a commanded rotation around the world z-axis,
+	 * yaw_sp_move_rate is the feed forward commanded rotation around the world z-axis,
 	 * but we need to apply it in the body frame (because _rates_sp is expressed in the body frame).
 	 * Therefore we infer the world z-axis (expressed in the body frame) by taking the last column of R.transposed (== q.inversed)
-	 * and multiply it by the yaw setpoint rate (yaw_sp_move_rate) and gain (_yaw_ff).
+	 * and multiply it by the yaw setpoint rate (yaw_sp_move_rate).
 	 * This yields a vector representing the commanded rotatation around the world z-axis expressed in the body frame
 	 * such that it can be added to the rates setpoint.
 	 */
-	Vector3f yaw_feedforward_rate = q.inversed().dcm_z();
-	yaw_feedforward_rate *= _v_att_sp.yaw_sp_move_rate * _yaw_ff.get();
-	_rates_sp += yaw_feedforward_rate;
+	_rates_sp += q.inversed().dcm_z() * _v_att_sp.yaw_sp_move_rate;
 
 
 	/* limit rates */

src/modules/mc_att_control/mc_att_control_params.c

@@ -263,19 +263,6 @@ PARAM_DEFINE_FLOAT(MC_YAWRATE_D, 0.0f);
  */
 PARAM_DEFINE_FLOAT(MC_YAWRATE_FF, 0.0f);
 
-/**
- * Yaw feed forward
- *
- * Feed forward weight for manual yaw control. 0 will give slow responce and no overshot, 1 - fast responce and big overshot.
- *
- * @min 0.0
- * @max 1.0
- * @decimal 2
- * @increment 0.01
- * @group Multicopter Attitude Control
- */
-PARAM_DEFINE_FLOAT(MC_YAW_FF, 0.5f);
-
 /**
  * Max roll rate
  *