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.c b/net/mac80211/mesh.c
index b3a125f..ee82d2f 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -366,7 +366,7 @@
 		return -ENOMEM;
 
 	pos = skb_put(skb, 2 + sizeof(struct ieee80211_ht_cap));
-	ieee80211_ie_build_ht_cap(pos, sband, sband->ht_cap.cap);
+	ieee80211_ie_build_ht_cap(pos, &sband->ht_cap, sband->ht_cap.cap);
 
 	return 0;
 }