nl80211: External authentication in driver-based AP SME mode

nl80211: External authentication in driver-based AP SME mode

This extends driver interface to nl80211 by introducing the following
changes,
1. Register for Authenication frames in driver-based AP SME mode.
2. Advertise NL80211_ATTR_EXTERNAL_AUTH_SUPPORT in set_ap when
   offloaded SAE authentication is supported.
3. Extend the NL80211_CMD_EXTERNAL_AUTH interface to also send PMKID
   so that the drivers can respond to the PMKSA cached connection
   attempts from the stations avoiding the need to contact user space
   for all PMKID-based connections.
4. Send external auth status to driver only if it is a driver based
   SME solution.

Signed-off-by: Srinivas Dasari <dasaris@codeaurora.org>