Huxley LM6UU X-ends

Just a little redesign to the 'Huxley Fold Beef'd X axis LM6UU mount's ' from natko:
- x-idler: added a spacer for the bearing to work without washers
- x-motor: cut away additional material for the endstop-pusher and added an adjustable endstop bolt.

After printing just insert a M3-nut, a small spring and a M3-bolt to have a fine adjustable endstop. Make sure your endstop-switch is exactly below the screw.