Revert "Staging: olpc_dcon: Remove obsolete driver"

This reverts commit 82ef33af

.  It turns
out these machines are still out there, and the original patch broke
them.  So revert it, adding back the driver, so people's machines still
work properly.

Reported-by: James Cameron <quozl@laptop.org>
Cc: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>