Staging: add mimio xi driver

This patch adds the Mimio Xi interactive whiteboard driver to the tree.

It was originally written by mwilder@cs.nmsu.edu, but cleaned up and
forward ported by me to the latest kernel version.

Cc: Phil Hannent <phil@hannent.co.uk>
Cc: <mwilder@cs.nmsu.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>