staging: comedi: adl_pci9118: tidy up analog output register defines

Replace the current defines with a macro that calculates the correct
register offset based on the channel.

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>

diff --cc drivers/staging/comedi/drivers/adl_pci9118.c
Simple merge