staging: comedi: ni_labpc: clean up register map

Rename the register map defines to better match the National
Instruments Register-Level Programming Manual for the labpc.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>