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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>