usbip: remove struct usb_device_id table

This was used back when usbip-host was an interface device driver;
after the conversion to device driver, the table remained unused.
Remove it in order to stop receiving a warning about it.

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