staging: comedi: adl_pci9118: tidy up the ai status register bit defines

Rename the CamelCase defines used for the analog input status register
bits and convert them to bit shifts.

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>