staging: comedi: daqboard2000: rename register offset macros

Rename the macros defining register offsets to avoid CamelCase, and to
use namespace associated with the driver.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>