mac80211: fix netdev rename

Fix a copy bug introduced by

    commit 47846c9b
    Author: Johannes Berg <johannes@sipsolutions.net>
    Date:   Wed Nov 25 17:46:19 2009 +0100

        mac80211: reduce reliance on netdev

This manifested itself only in debug messages
and in the debugfs rename failure that would
always happen due to trying to rename the dir
over itself.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Tested-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>