mac80211: Support ht-cap over-rides.

This implements ht-cap over-rides for mac80211 drivers.
HT may be disabled, making an /a/b/g/n station act like an
a/b/g station.  HT40 may be disabled forcing the station to
be HT20 even if the AP and local hardware support HT40.

MAX-AMSDU may be disabled.
AMPDU-Density may be increased.
AMPDU-Factor may be decreased.

This has been successfully tested with ath9k using patched
wpa_supplicant and iw.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 0140e88..7314372b 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -101,7 +101,8 @@
 	set_sta_flag(sta, WLAN_STA_WME);
 	sta->sta.supp_rates[local->hw.conf.channel->band] = rates;
 	if (elems->ht_cap_elem)
-		ieee80211_ht_cap_ie_to_sta_ht_cap(sband, elems->ht_cap_elem,
+		ieee80211_ht_cap_ie_to_sta_ht_cap(sdata, sband,
+						  elems->ht_cap_elem,
 						  &sta->sta.ht_cap);
 	rate_control_rate_init(sta);