[FR] Add E-Mot header to FFC-X-Mot board

[pyr0ball]

Currently the FFC cable chain only supports Direct Drive extruders (on-head), but it would be fairly trivial to add a second stepper header to the X-Motor board to allow users to utilize the same PCB for extruder steppers that live on the same mount as the X-Motor (as in the Creality Ender3/CR-10 family)