Previously, both CONFIG_IEEE80211W=y and CONFIG_IEEE80211R=y were needed
to enable SHA256-based key handshake (WPA-PSK-SHA256 and
WPA-EAP-SHA256). This can now be done with just CONFIG_IEEE80211W=y.
IEEE 802.11w/D6.0 defines new AKMPs to indicate SHA256-based algorithms for
key derivation (and AES-CMAC for EAPOL-Key MIC). Add support for using new
AKMPs and clean up AKMP processing with helper functions in defs.h.
