staging: olpc_dcon: remove outdated backlight comment

This comment about killing power to the backlight is ancient, and incorrect
(the code that follows actually does the opposite of what the comment says).
This was due to hardware changes; the comment was for the original OLPC GX2
boards, but when the OLPC LX boards came out, the code was updated for that
hardware.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>