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.
This adds most of the new frame format and identifier definitions from IEEE
802.11w/D6.0. In addition, the RSN IE capability field values for MFP is
replaced with the new two-bit version with MFPC (capable) and MFPR
(required) processing.
