Staging: comedi: set up infrastructure for individual drivers

This adds two "generic" Kconfig options, one for PCI and one for USB
comedi drivers, and the Makefile infrastructure as well.  This is so
we can start adding individual comedi drivers and add them to the build
properly.

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