AP/GO interface teardown optimization

AP/GO interface teardown optimization

This commit adds an option to optimize AP teardown by leaving the
deletion of keys (including group keys) and stations to the driver.

This optimization option should be used if the driver supports stations
and keys removal when stopping an AP.

For example, the optimization option will always be used for cfg80211
drivers since cfg80211 shall always remove stations and keys when
stopping an AP (in order to support cases where the AP is disabled
without the knowledge of wpa_supplicant/hostapd).

Signed-off-by: Moshe Benji <moshe.benji@intel.com>