ieee80211: update HE IEs to D4.0 spec

Update the out-dated comments as well, and have them point to
the correct sections in the D4.0 spec.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>