Add support for Z encoder pulse homing on DC motor

[DrFrankReade]

Homing for DC motors on Z-pulse doesn't usually work, and not predictable, sometimes producing a runaway, sometimes producing a reversed encoder error, and sometimes I gently turn the wheel at powerup and it springs into perfect action. Behavior exists on TMC driver in DC motor mode, and in PWM drive mode to basic DC motor drivers. Likely exists with others. Behavior seems as though this feature has not been fully implemented or tested but exists in a preliminary form.

Few people currently use DC motors, however, with the recent discovery of the excellent performance characteristics of electric power steering columns that feature DC motors for this FFB application, the community will begin to find value in this feature.