staging: usbip: userspace: rename usbip device and interface

Add prefix of usbip_ to internal usb device and interface to avoid
confusion with the kernel types. This also identifies the types as
being part of the usbip library.

Signed-off-by: matt mooney <mfm@muteddisk.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>