Airspeed fix attempt
Mag scale check: only test if the scale roughly makes sense, do not judge the environment
Time out after a reasonable interval (10 seconds, as e.g. OBC rules prescribe). Experiments show the SiK radios to time out ~4-7 seconds if they loose sync
Do not perform retries in airspeed driver - this is too much load for the HRT queue
Merge branch 'master' of github.com:PX4/Firmware into as_fix
Merge pull request #1292 from PX4/as_fix

Airspeed fix attempt
Merge pull request #1293 from PX4/timeout_fix

Timeout fix
Merge branch 'master' of https://github.com/PX4/Firmware