staging: ozwpan: Added USB service to protocol

The L2 protocol supports various services, one of which is USB.
This provides the implementation of that service and plumbs it to
the virtual USB HCD.

Signed-off-by: Chris Kelly <ckelly@ozmodevices.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>