staging: comedi: daqboard2000: rename acquisition control register macros

Rename the macros defining values for the acquisition control register
to avoid CamelCase, and to make it clearer which register they are
associated with.

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>