BACKPORT: cfg80211: Support key configuration for Beacon protection (BIGTK)

IEEE P802.11-REVmd/D3.0 adds support for protecting Beacon frames using
a new set of keys (BIGTK; key index 6..7) similarly to the way
group-addressed Robust Management frames are protected (IGTK; key index
4..5). Extend cfg80211 and nl80211 to allow the new BIGTK to be
configured. Add an extended feature flag to indicate driver support for
the new key index values to avoid array overflows in driver
implementations and also to indicate to user space when this
functionality is available.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200222132548.20835-2-jouni@codeaurora.org


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
(cherry picked from commit 56be393fa8b40db2d4f54f97614f645eb8d3c32e)
[connoro: resolve conflicts; add preceding enum values to preserve
uapi; drop changes to lines not present in 4.19]
Bug: 154523213
Signed-off-by: Connor O'Brien <connoro@google.com>
Change-Id: Iab2dff167159556167600a88091a8e6b28db4ad8