staging: comedi: comedi_parport: tidy up parport_insn_c()

Rename this function to better describe it's use.

Use comedi_dio_update_state() to handle the boilerplate code to update
the subdevice s->state.

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>