staging: comedi: pcl726: tidy up pcl726_attach()

For aesthetics, add some whitespace to the subdevice initialization.

Only allocate, and initialize, the digital input and output subdevices
if the boardinfo indicates that they exist on the board.

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>