= use ELE_IN as the reference RX channel to synchronize the servo output frame.
- both v1 and v2 use ELE_IN (PIN 9 or PB1) in all mix variants (normal, delta, vtail).
- keep the timeout of 30ms anyways, to generate the servo pulses if there are no rx pulses.
- note: all these should be going away with the channel-level sync changes.