iwlwifi: mvm: include configured sniffer AID in radiotap

In order to make more sense out of the captured radiotap data e.g.
when the configured AID changes, add the currently configured AID
to the radiotap data as a vendor extension field.

This is made race-free by updating the included value from inside
the RX path (using a notification wait) for the command response
from the firmware, which thus means it's serialized with frame RX.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>