Staging: comedi: add ii_pci20kc driver

Driver for Intelligent Instruments PCI-20001C carrier board
and modules.

From: Markus Kempf <kempf@matsci.uni-sb.de>
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>