Unregister device from system.
void device_unregister(struct device * dev);
dev
device going away.
We do this in two parts, like we do device_register. First, we remove it from all the subsystems with device_del, then we decrement the reference count via put_device. If that is the final reference count, the device will be cleaned up via device_release above. Otherwise, the structure will stick around until the final reference to the device is dropped.