staging: comedi: comedi_parport: tidy up parport_insn_b()

Rename this function to better describe it's use.

Tidy it up to follow the normal comedi (*insn_bits) for DI subdevices.

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>