staging: comedi: pcl726: final tidy up of boardinfo

For aesthetics, rearrange the boardinfo struct definition a bit to give
it a bit of logical order.

Also, rename the 'n_aochan' member to it has better visual association
with the other analog output members.

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>