* EKF2 split output predictor and publish attitude immediately

* ecl: incorporate magic number tidy up

This frees unused RAM in case frsky telemetry is not connected.

If S.Port is connected via external inverter or an uninverted signal is
used, the UART needs to be put into half-duplex mode.

This can be used to get uninverted S.Port:
https://oscarliang.com/uninverted-sbus-smart-port-frsky-receivers/

It is not needed for the Pixracer FrSky port.

As indicated in previous logs (268 bytes left).