cfg80211: Add feature flag for Fast Initial Link Setup (FILS) as STA

This defines a feature flag that drivers can use to indicate that they
support FILS authentication/association (IEEE 802.11ai) when using user
space SME (NL80211_CMD_AUTHENTICATE) in station mode.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Git-commit: 60b8084e844814631b57da3d35f272e0ff799ab2
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git
CRs-Fixed: 1112321
Change-Id: Ifd67a5fe9959ac96ce04135d55a7ae2ccacd028f