cfg80211: remove dead variable

commit 211a4d12abf86fe0df4cd68fc6327cbb58f56f81
  Author: Johannes Berg <johannes@sipsolutions.net>
  Date:   Tue Oct 20 15:08:53 2009 +0900

      cfg80211: sme: deauthenticate on assoc failure

accidentally introduced a dead variable, I had
changed the code to not need it while creating
the patch and it looks like I forgot to remove
the variable (and nobody else noticed either).

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>