staging: comedi: usbdux: generalize the usb_submit_urb functions

Generalize a helper function to replace usbduxsub_submit_{in,out}urbs().

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>