device_destroy — 
     removes a device that was created with device_create
 
| void device_destroy ( | struct class * class, | 
| dev_t devt ); | 
classpointer to the struct class that this device was registered with
devtthe dev_t of the device that was previously registered
   This call unregisters and cleans up a device that was created with a
   call to device_create.