wifi: mac80211: fix error path key leak

In the previous key leak fix for the other error
paths, I meant to unify all of them to the same
place, but used the wrong label, which I noticed
when doing the merge into wireless-next. Fix it.

Fixes: d097ae01 ("wifi: mac80211: fix potential key leak")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>