Copter: remove enable_motor_output method

this doesn't actually do what it says it does.  I think the functionality to set the motors armed was split out long ago but this little method and its misleading comments remained

ArduCopter/AP_Arming.cpp

@@ -755,8 +755,8 @@ bool AP_Arming_Copter::arm(const AP_Arming::Method method, const bool do_arming_
     copter.sprayer.test_pump(false);
 #endif
 
-    // enable output to motors
-    copter.enable_motor_output();
+    // output lowest possible value to motors
+    copter.motors->output_min();
 
     // finally actually arm the motors
     copter.motors->armed(true);

ArduCopter/Copter.h

@@ -891,7 +891,6 @@ private:
     void default_dead_zones();
     void init_rc_in();
     void init_rc_out();
-    void enable_motor_output();
     void read_radio();
     void set_throttle_and_failsafe(uint16_t throttle_pwm);
     void set_throttle_zero_flag(int16_t throttle_control);

ArduCopter/compassmot.cpp

@@ -123,7 +123,7 @@ MAV_RESULT Copter::mavlink_compassmot(const GCS_MAVLINK &gcs_chan)
     EXPECT_DELAY_MS(5000);
 
     // enable motors and pass through throttle
-    enable_motor_output();
+    motors->output_min();  // output lowest possible value to motors
     motors->armed(true);
     hal.util->set_soft_armed(true);
 

ArduCopter/motor_test.cpp

@@ -153,7 +153,7 @@ MAV_RESULT Copter::mavlink_motor_test_start(const GCS_MAVLINK &gcs_chan, uint8_t
             EXPECT_DELAY_MS(3000);
             // enable and arm motors
             if (!motors->armed()) {
-                enable_motor_output();
+                motors->output_min();  // output lowest possible value to motors
                 motors->armed(true);
                 hal.util->set_soft_armed(true);
             }

ArduCopter/radio.cpp

@@ -77,13 +77,6 @@ void Copter::init_rc_out()
 }
 
 
-// enable_motor_output() - enable and output lowest possible value to motors
-void Copter::enable_motor_output()
-{
-    // enable motors
-    motors->output_min();
-}
-
 void Copter::read_radio()
 {
     const uint32_t tnow_ms = millis();

ArduCopter/system.cpp

@@ -208,7 +208,7 @@ void Copter::init_ardupilot()
 
     // enable output to motors
     if (arming.rc_calibration_checks(true)) {
-        enable_motor_output();
+        motors->output_min();  // output lowest possible value to motors
     }
 
     // attempt to set the intial_mode, else set to STABILIZE