AP_DAL: add define AP_AIRSPEED_ENABLED

libraries/AP_DAL/AP_DAL.cpp

@@ -129,10 +129,12 @@ void AP_DAL::init_sensors(void)
         alloc_failed |= (_rangefinder = new AP_DAL_RangeFinder) == nullptr;
     }
 
+#if AP_AIRSPEED_ENABLED
     auto *aspeed = AP::airspeed();
     if (aspeed != nullptr && aspeed->get_num_sensors() > 0) {
         alloc_failed |= (_airspeed = new AP_DAL_Airspeed) == nullptr;
     }
+#endif
 
     auto *bcn = AP::beacon();
     if (bcn != nullptr && bcn->enabled()) {

libraries/AP_DAL/AP_DAL_Airspeed.cpp

@@ -5,13 +5,16 @@
 
 AP_DAL_Airspeed::AP_DAL_Airspeed()
 {
+#if AP_AIRSPEED_ENABLED
     for (uint8_t i=0; i<ARRAY_SIZE(_RASI); i++) {
         _RASI[i].instance = i;
     }
+#endif
 }
 
 void AP_DAL_Airspeed::start_frame()
 {
+#if AP_AIRSPEED_ENABLED
     const auto *airspeed = AP::airspeed();
     if (airspeed == nullptr) {
         return;
@@ -31,4 +34,5 @@ void AP_DAL_Airspeed::start_frame()
         RASI.airspeed = airspeed->get_airspeed(i);
         WRITE_REPLAY_BLOCK_IFCHANGED(RASI, RASI, old_RASI);
     }
+#endif
 }