MotionPlanner: fix inefficiency when homing. When an endstop is pressed, we don't need to send any remaining buffered motion through the planner and into execution, only to find yet again that the endstop is pressed.
MotionPlanner: fix inefficiency when homing.
When an endstop is pressed, we don't need to send any remaining
buffered motion through the planner and into execution, only to find yet
again that the endstop is pressed.

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