If a network configuration block is removed or modified, flush
all PMKSA cache entries that were created using that network
configuration. Similarly, invalidate EAP state (fast re-auth).
The special case for OKC on wpa_supplicant reconfiguration
(network_ctx pointer change) is now addressed as part of the
PMKSA cache flushing, so it does not need a separate mechanism
for clearing the network_ctx values in the PMKSA cache.
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.
