Move all the usb buffer allocation code in the usb_driver (*probe)
into a new function, usbdux_alloc_usb_buffers(). This allows tidying
up the error path in the (*probe).
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>