When the usb device is disconnected, the resources are no longer available,
so there is no reason to keep them registered.

This will also fix the various sysfs group removal warnings which we can see
since kernel 3.13.
Signed-off-by: NFrank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>