mac80211: clean up key freeing a bit

When a key is allocated but not really added, there's no
need to go through the entire teardown process. Also, if
adding a key fails, ieee80211_key_link() can take care of
freeing it instead of the (only) caller.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc net/mac80211/cfg.c
Simple merge

diff --cc net/mac80211/key.c
Simple merge

diff --cc net/mac80211/key.h
Simple merge