AP_Mount: add HAL_MOUNT_SERVO_ENABLED build option

libraries/AP_Mount/AP_Mount.cpp

@@ -443,8 +443,10 @@ void AP_Mount::init()
 
         // check for servo mounts
         if (mount_type == Mount_Type_Servo) {
+#if HAL_MOUNT_SERVO_ENABLED
             _backends[instance] = new AP_Mount_Servo(*this, state[instance], instance);
             _num_instances++;
+#endif
 
 #if HAL_SOLO_GIMBAL_ENABLED
         // check for MAVLink mounts

libraries/AP_Mount/AP_Mount_Servo.cpp

@@ -1,5 +1,5 @@
 #include "AP_Mount_Servo.h"
-#if HAL_MOUNT_ENABLED
+#if HAL_MOUNT_SERVO_ENABLED
 
 extern const AP_HAL::HAL& hal;
 
@@ -221,4 +221,4 @@ void AP_Mount_Servo::move_servo(uint8_t function_idx, int16_t angle, int16_t ang
 	int16_t servo_out = closest_limit(angle, angle_min, angle_max);
 	SRV_Channels::move_servo((SRV_Channel::Aux_servo_function_t)function_idx, servo_out, angle_min, angle_max);
 }
-#endif // HAL_MOUNT_ENABLED
+#endif // HAL_MOUNT_SERVO_ENABLED

libraries/AP_Mount/AP_Mount_Servo.h

@@ -3,13 +3,19 @@
  */
 #pragma once
 
+#include "AP_Mount_Backend.h"
+
+#ifndef HAL_MOUNT_SERVO_ENABLED
+#define HAL_MOUNT_SERVO_ENABLED HAL_MOUNT_ENABLED
+#endif
+
+#if HAL_MOUNT_SERVO_ENABLED
+
 #include <AP_Math/AP_Math.h>
 #include <AP_Common/AP_Common.h>
 #include <AP_AHRS/AP_AHRS.h>
 #include <GCS_MAVLink/GCS_MAVLink.h>
 #include <SRV_Channel/SRV_Channel.h>
-#include "AP_Mount_Backend.h"
-#if HAL_MOUNT_ENABLED
 
 class AP_Mount_Servo : public AP_Mount_Backend
 {
@@ -71,4 +77,4 @@ private:
 
     uint32_t _last_check_servo_map_ms;  // system time of latest call to check_servo_map function
 };
-#endif // HAL_MOUNT_ENABLED
+#endif // HAL_MOUNT_SERVO_ENABLED