mac80211_hwsim: Extended Key ID support

Allow Extended Key ID to be used with hwsim.

Hwsim can only communicate with other hwsim cards, allowing it to bypass
creation of A-MPDUs in the first place.

Mixing keyIDs in an A-MPDU is therefore impossible and can never cause
interoperability issues with other cards.

Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
[reword comment slightly]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>