cfg80211: Changes to support key managment offload

These changes represent a small number of extensions to the nl80211/
cfg80211 interface to support the offload of key management to the
device.

A discussion of the key management offload feature including what
it does and how it is used can be found in the file
Documentation/networking/key-mgmt-offload.txt.  Also, details of
the changes being submitted here and how they implement key
management offload can be found in that file.

CRs-Fixed: 692546
Change-Id: Ie521dc9df791cac731d1d956f349ddac6319a96c
Signed-off-by: Chet Lanctot <clanctot@codeaurora.org>