MotionPlanner: don't reserve more stepper/channel commands than we actually need.
MotionPlanner: don't reserve more stepper/channel commands than we
actually need.

ambrop72/aprinter,johnkingsley/aprinter,fixator/aprinter,ambrop72/aprinter,johnkingsley/aprinter,ambrop72/aprinter,ambrop72/aprinter,fixator/aprinter,ambrop72/aprinter,ambrop72/aprinter,johnkingsley/aprinter,fixator/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,fixator/aprinter,fixator/aprinter,johnkingsley/aprinter,fixator/aprinter,ambrop72/aprinter