staging: comedi: adv_pci_dio: convert boardinfo initialization to C99 format

Convert the boardinfo initialization to C99 format to make it
less error prone.

The struct diosubd_data information is not converted to C99 format
yet because some of it will be removed.

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>