staging: comedi: ni_labpc: rename some of the private data variables

For aesthetic reasons, rename the 'command*_bits' and 'status*_bits'
variables in the private data in order to shorten some of the long
lines.

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