mac80211: add vendor-specific capabilities to assoc request

When sending an association request, add any vendor specific
capabilities at the end of the frame. This way, mac80211 is
still completely in charge of building the frame, but drivers
can determine what should be added depending on the band and
interface type.

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.20210618133832.80d716d69a5f.I28097ff19be6b22aebdc33a72795d2662755d41f@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>