AP_Proximity: change AC_FENCE to AP_FENCE_ENABLED

libraries/AP_Proximity/AP_Proximity_SITL.cpp

@@ -51,7 +51,7 @@ void AP_Proximity_SITL::update(void)
     current_loc.lng = sitl->state.longitude * 1.0e7;
     current_loc.alt = sitl->state.altitude * 1.0e2;
 
-#if AC_FENCE
+#if AP_FENCE_ENABLED
     if (!AP::fence()->polyfence().breached()) {
         // only called to prompt polyfence to reload fence if required
     }
@@ -81,7 +81,7 @@ void AP_Proximity_SITL::update(void)
 // get distance in meters to fence in a particular direction in degrees (0 is forward, angles increase in the clockwise direction)
 bool AP_Proximity_SITL::get_distance_to_fence(float angle_deg, float &distance) const
 {
-#if AC_FENCE
+#if AP_FENCE_ENABLED
     if (!AP::fence()->polyfence().inclusion_boundary_available()) {
         return false;
     }