cfg80211: send stop AP event only due to internal reason

Commit "nl80211: send event when AP operation is stopped" added an
event to notify user space that an AP interface has been stopped, to
handle cases such as suspend etc. The event is sent regardless
if the stop AP flow was triggered by user space or due to internal state
change.

This might cause issues with wpa_supplicant/hostapd flows that consider
stop AP flow as a synchronous one, e.g., AP/GO channel change in the
absence of CSA support. In such cases, the flow will restart the AP
immediately after the stop AP flow is done, and only handle the stop
AP event after the current flow is done, and as a result stop the AP
again.

Change the current implementation to only send the event in case the
stop AP was triggered due to an internal reason.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>