cfg80211: allow advertising vendor-specific capabilities

cfg80211: allow advertising vendor-specific capabilities

There may be cases where vendor-specific elements need to be
used over the air. Rather than have driver or firmware add
them and possibly cause problems that way, add them to the
iftype-data band capabilities. This way we can advertise to
userspace first, and use them in mac80211 next.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.e8c4f0347276.Iee5964682b3e9ec51fc1cd57a7c62383eaf6ddd7@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>