staging: comedi: pcl711: convert boardinfo declaration to C99 format

Convert the boardinfo declaration to C99 format to make it less error
prone and easier to maintain.

For aesthetics, move the declaration closer to the struct definition.

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>