staging: comedi: pcl818: change 'is_818' in boardinfo to a bit-field

Change this flag in the boardinfo into a bit-field.

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>