staging: comedi: ni_labpc: don't pass dev->iobase to labpc_counter_set_mode()

Use the comedi_device parameter that is passed to this function to find
the dev->iobase so it does not have to be included in each call.

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>