Enumerates the PRU UIO Devices's on a BeagleBone Black.
public enum PRUUIODeviceEnum { PRUUIODEVICE_NONE, PRUUIODEVICE_0, PRUUIODEVICE_1, PRUUIODEVICE_2, PRUUIODEVICE_3, PRUUIODEVICE_4, PRUUIODEVICE_5, PRUUIODEVICE_6, PRUUIODEVICE_7 }