Add support for phase/enable driver interface.

DC motor drivers like the [DRV8256E](https://www.ti.com/lit/ds/symlink/drv8256.pdf) use a phase/enable interface. This interface requires a single PWM "enable" signal and a direction (phase) signal, as opposed to the dual-PWM IN/IN interface used by drivers like the Adafruit DRV8833. From what I can tell, this library doesn't currently support the phase/enable interface, only the IN/IN interface.

The first question is: Am I overlooking something?

If not, I have a [fork](https://github.com/adafruit/Adafruit_CircuitPython_Motor/compare/main...lcmcninch:Adafruit_CircuitPython_Motor:main) that enhances the `DCMotor` class to optionally support this driver interface. I'm not sure how common this type of driver is. Would you be interested in a pull request with these changes?

Start by reading the DCMotor class and compare its current interface handling with the linked fork. Confirm whether phase/enable drivers are already supported, then evaluate the fork's optional support for a PWM enable signal and direction signal. Done means the library supports this interface without regressing dual-PWM IN/IN drivers; no test file is named in the issue.

Written by the indexing model from the issue text.