usb: ohci-pxa27x: add explicit include of hardware.h

ohci-pxa27x needs cpu_is_pxa3xx macro.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Cc: linux-kernel@vger.kernel.org