mac80211: handle protection mode, RIFS and ADDBA for HT IBSS

* Follow 802.11n-2009 9.13.3.1 for protection mode and ADDBA
* Send ADDBA only to HT STAs - implement 11.5.1.1 partially

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 5243c2c..ac7ea29 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1587,6 +1587,11 @@
 	}
 	if (ht_cap->cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40)
 		ht_info->ht_param |= IEEE80211_HT_PARAM_CHAN_WIDTH_ANY;
+
+	/*
+	 * Note: According to 802.11n-2009 9.13.3.1, HT Protection field and
+	 * RIFS Mode are reserved in IBSS mode, therefore keep them at 0
+	 */
 	ht_info->operation_mode = 0x0000;
 	ht_info->stbc_param = 0x0000;