commit b27c0d0c upstream.

"calibrate" attribute does not provide "show" methods and thus we should
not mark it as readable.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>