Airspeed driver: Use the known sensor offset for raw value as well

src/drivers/ets_airspeed/ets_airspeed.cpp

@@ -172,6 +172,9 @@ ETSAirspeed::collect()
 		diff_pres_pa = diff_pres_pa_raw - _diff_pres_offset;
 	}
 
+	// The raw value still should be compensated for the known offset
+	diff_pres_pa_raw -= _diff_pres_offset;
+
 	// Track maximum differential pressure measured (so we can work out top speed).
 	if (diff_pres_pa > _max_differential_pressure_pa) {
 		_max_differential_pressure_pa = diff_pres_pa;

src/drivers/meas_airspeed/meas_airspeed.cpp

@@ -225,7 +225,10 @@ MEASAirspeed::collect()
         // correct for 5V rail voltage if possible
         voltage_correction(diff_press_pa_raw, temperature);
 
-	float diff_press_pa = fabsf(diff_press_pa_raw - _diff_pres_offset);
+	// the raw value still should be compensated for the known offset
+	diff_press_pa_raw -= _diff_pres_offset;
+
+	float diff_press_pa = fabsf(diff_press_pa_raw);
 	
 	/*
 	  note that we return both the absolute value with offset