staging: comedi: cb_pcidas: tidy up dac08_write()

Rename this function so it has namespace associated with the driver.
Also rename the 'value' parameter to avoid having to split the line
to keep it under 80 chars.

Remove the unnecessary masking on the 'value'.

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>