staging: usbip: remove unnused, broken macro

Remove broken preprocessor macro "hardware". It is unused and it
references an element (pdev in vhci_hcd) that does not exist.

Signed-off-by: Stefan Reif <ke42caxa@cip.cs.fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>