mac80211: move AP teardown code to correct place

Since cfg80211 will now call the explicit stop_ap
operation when an AP interface goes down, move all
teardown code there and remove it from interface
handling. The only thing that needs to stay is the
code to dev_close() all dependent VLANs.

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

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

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