nl80211: fix possible memory leak nl80211_connect()

connkeys is malloced in nl80211_parse_connkeys() and should
be freed in the error handling case, otherwise it will cause
memory leak.

spatch with a semantic match is used to found this problem.
(http://coccinelle.lip6.fr/)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>