ieee80211_add_htcap_vendor
frm = ieee80211_add_htcap_vendor(frm, in);
frm = ieee80211_add_htcap_vendor(frm, in);
frm = ieee80211_add_htcap_vendor(frm, in);
uint8_t *ieee80211_add_htcap_vendor(uint8_t *, struct ieee80211_node *);