staging: usbip: userspace: remove class device infrastructure in vhci_driver

The class device lists were used only when being initialized,
being populated and being destroyed. They had no real meaning
and thus the code was useless.

Signed-off-by: Valentina Manea <valentina.manea.m@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>