net80211: add initial key management suites from 802.11-2016, APIs to register them

The WPA1/WPA2 driver capabilities aren't really enough in today's world.
There are a /lot/ more key management suites to support!

So, add initial support for net80211 and drivers to announce what
key management suites are supported. These are the list from 802.11-2016
section 9.4.2.25.3 (AKM suites.)

The flags are for software supported key management.

Drivers may support more key management suites and are welcome to
announce more; net80211 will only announce ones that we know
net80211 knows "enough" about to support correctly.

There /are/ other suites that may be interesting to some people in
the future that are not part of this set - eg if anyone ever
wants to support the Chinese WAPI standard - so this bitmap is not
specifically just the AKM suites in the RSN OUI.

This should eventually be communicated up to the wpa_supplicant and
hostapd via a replacement driver/vap capabilities call so they know
what to enable rather than just IEEE80211_C_WPA1 / IEEE80211_C_WPA2.

Differential Revision: https://reviews.freebsd.org/D44919
Reviewed by: bz