AP_Frsky_Telem: get airspeed sensor from singleton not AHRS object

libraries/AP_Frsky_Telem/AP_Frsky_SPort_Passthrough.cpp

@@ -516,7 +516,7 @@ uint32_t AP_Frsky_SPort_Passthrough::calc_velandyaw(void)
     AP_AHRS &_ahrs = AP::ahrs();
     WITH_SEMAPHORE(_ahrs.get_semaphore());
     // horizontal velocity in dm/s (use airspeed if available and enabled - even if not used - otherwise use groundspeed)
-    const AP_Airspeed *aspeed = _ahrs.get_airspeed();
+    const AP_Airspeed *aspeed = AP::airspeed();
     if (aspeed && aspeed->enabled()) {
         velandyaw |= prep_number(roundf(aspeed->get_airspeed() * 10), 2, 1)<<VELANDYAW_XYVEL_OFFSET;
     } else { // otherwise send groundspeed estimate from ahrs