O2_2 (Second probe data) not being logged

[gdiciocco]

Additional lambda probe data is currently not being logged, it can only be seen in TS in realtime. It's just unreferenced in speeduino.ini logging section and adding it would be straightforward, pr #732 already includes this.

eventually one can add it by adding: entry = afr2, "AFR 2", float, "%.3f"
to speeduino.ini:5129