drivers: minimize additional I2C retries

src/lib/drivers/airspeed/airspeed.cpp

@@ -104,11 +104,9 @@ Airspeed::probe()
 	   for detection. Once it is running the number of retries can
 	   be reduced
 	*/
-	_retries = 4;
+	_retries = 1;
 	int ret = measure();
 
-	// drop back to 2 retries once initialised
-	_retries = 2;
 	return ret;
 }