The light sensor disable brightness key and
/sys/class/backlight/ control. There was a lot of report
from users who didn't understand why they couldn't change their
brightness, including:

https://bugs.launchpad.net/bugs/222171
https://bugzilla.novell.com/show_bug.cgi?id=514747
http://bugzilla.kernel.org/show_bug.cgi?id=13671
http://bugzilla.kernel.org/show_bug.cgi?id=14432

Now the light sensor is disabled, and if the user want to enable
it, the level should be ok.

The funny thing is that comments where ok, not code.

Cc: stable@kernel.org
Cc: Thomas Renninger <trenn@suse.de>
Cc: Peter Küppers <peter-mailbox@web.de>
Cc: Michael Franzl <michaelfranzl@gmx.at>
Cc: Ian Turner <vectro@vectro.org>
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Len Brown <len.brown@intel.com>