Staging: comedi: add s626 driver

This adds the s626 comedi driver to the build.

From: Gianluca Palli <gpalli@deis.unibo.it>
Cc: David Schleef <ds@schleef.org>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>