Support Extended Key ID in hostapd according to IEEE Std 802.11-2016.
Extended Key ID allows to rekey pairwise keys without the otherwise
unavoidable MPDU losses on a busy link. The standard is fully backward
compatible, allowing an AP to serve STAs with and without Extended Key
ID support in the same BSS.
Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>