AP_MotorsCoax: rename _rev_roll to _roll_reverse

Also rename _rev_pitch to _pitch_reverse and _rev_yaw to _yaw_reverse

libraries/AP_Motors/AP_MotorsCoax.cpp

@@ -39,19 +39,19 @@ const AP_Param::GroupInfo AP_MotorsCoax::var_info[] = {
     // @DisplayName: Reverse roll feedback 
     // @Description: Ensure the feedback is negative
     // @Values: -1:Reversed,1:Normal
-    AP_GROUPINFO("ROLL_SV_REV", 40, AP_MotorsCoax, _rev_roll, AP_MOTORS_COAX_POSITIVE),
+    AP_GROUPINFO("ROLL_SV_REV", 40, AP_MotorsCoax, _roll_reverse, AP_MOTORS_COAX_POSITIVE),
 
     // @Param: PITCH_SV_REV
     // @DisplayName: Reverse roll feedback 
     // @Description: Ensure the feedback is negative
     // @Values: -1:Reversed,1:Normal
-    AP_GROUPINFO("PITCH_SV_REV", 41, AP_MotorsCoax, _rev_pitch, AP_MOTORS_COAX_POSITIVE),
+    AP_GROUPINFO("PITCH_SV_REV", 41, AP_MotorsCoax, _pitch_reverse, AP_MOTORS_COAX_POSITIVE),
 
 	// @Param: YAW_SV_REV
     // @DisplayName: Reverse roll feedback 
     // @Description: Ensure the feedback is negative
     // @Values: -1:Reversed,1:Normal
-    AP_GROUPINFO("YAW_SV_REV", 42, AP_MotorsCoax, _rev_yaw, AP_MOTORS_COAX_POSITIVE),
+    AP_GROUPINFO("YAW_SV_REV", 42, AP_MotorsCoax, _yaw_reverse, AP_MOTORS_COAX_POSITIVE),
 
 	// @Param: SV_SPEED
     // @DisplayName: Servo speed 

libraries/AP_Motors/AP_MotorsCoax.h

@@ -60,9 +60,10 @@ protected:
     // output - sends commands to the motors
     void                output_armed_stabilizing();
 
-    AP_Int8             _rev_roll;      // REV Roll feedback
-    AP_Int8             _rev_pitch;     // REV pitch feedback
-    AP_Int8             _rev_yaw;       // REV yaw feedback
+    // We shouldn't need roll, pitch, and yaw reversing with servo reversing.
+    AP_Int8             _roll_reverse;  // Reverse roll output
+    AP_Int8             _pitch_reverse; // Reverse pitch output
+    AP_Int8             _yaw_reverse;   // Reverse yaw output
     AP_Int16            _servo_speed;   // servo speed
     RC_Channel&         _servo1;
     RC_Channel&         _servo2;