staging: comedi: das16m1: tidy up control/status register defines

Rename the defines for the control/status register/bits. Use the BIT
macro to define the bits.

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>