AP_MotorsMulticopter: remove slow_start

This has been replaced with the spool logic feature

libraries/AP_Motors/AP_MotorsMulticopter.cpp

@@ -122,10 +122,6 @@ AP_MotorsMulticopter::AP_MotorsMulticopter(uint16_t loop_rate, uint16_t speed_hz
     // disable all motors by default
     memset(motor_enabled, false, sizeof(motor_enabled));
 
-    // init flags
-    _multicopter_flags.slow_start = false;
-    _multicopter_flags.slow_start_low_end = true;
-
     // setup battery voltage filtering
     _batt_voltage_filt.set_cutoff_frequency(AP_MOTORS_BATT_VOLT_FILT_HZ);
     _batt_voltage_filt.reset(1.0f);
@@ -318,7 +314,6 @@ void AP_MotorsMulticopter::output_logic()
     if (!_flags.armed || !_flags.interlock) {
         _spool_desired = DESIRED_SHUT_DOWN;
         _multicopter_flags.spool_mode = SHUT_DOWN;
-        _multicopter_flags.slow_start_low_end = true;
     }
 
     switch (_multicopter_flags.spool_mode) {
@@ -469,14 +464,6 @@ void AP_MotorsMulticopter::output_logic()
     }
 }
 
-// slow_start - set to true to slew motors from current speed to maximum
-// Note: this must be set immediately before a step up in throttle
-void AP_MotorsMulticopter::slow_start(bool true_false)
-{
-    // set slow_start flag
-    _multicopter_flags.slow_start = true;
-}
-
 // throttle_pass_through - passes provided pwm directly to all motors - dangerous but used for initialising ESCs
 //  pwm value is an actual pwm value that will be output, normally in the range of 1000 ~ 2000
 void AP_MotorsMulticopter::throttle_pass_through(int16_t pwm)

libraries/AP_Motors/AP_MotorsMulticopter.h

@@ -75,10 +75,6 @@ public:
 
     void                output_logic();
 
-    // slow_start - set to true to slew motors from current speed to maximum
-    // Note: this must be set immediately before a step up in throttle
-    void                slow_start(bool true_false);
-
     // throttle_pass_through - passes provided pwm directly to all motors - dangerous but used for initialising ESCs
     //  pwm value is an actual pwm value that will be output, normally in the range of 1000 ~ 2000
     void                throttle_pass_through(int16_t pwm);
@@ -139,8 +135,6 @@ protected:
     // flag bitmask
     struct {
         spool_up_down_mode     spool_mode       : 4;    // motor's current spool mode
-        uint8_t slow_start         : 1;    // 1 if slow start is active
-        uint8_t slow_start_low_end : 1;    // 1 just after arming so we can ramp up the spin_when_armed value
     } _multicopter_flags;
 
     // parameters