doc: update list of supported boards in hm2_pci manpage
docs: fix motion(9) motion.in-position pin name

Also expand the description of the pin meaning a little.
Default to on, as it makes tuning easier.

This will disturb existing tunings, so those with old configs who do not want
to re-tune may want to set pid.N.error-previous-target to false.
docs: update motion(9) to match reality

We haven't had a "motion.motion-inpos" pin since af317701 (January 2009).
docs: add missing motion.motion-type to motion(9) manpage
Merge remote-tracking branch 'origin/2.6'