Staging: comedi: add pcmda12 driver

Driver for Winsystems PC-104 based PCM-D/A-12 8-channel AO board.

From: Calin Culianu <calin@ajvar.org>
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>