nl80211: Add frequency configuration (including HT40)

This patch adds new NL80211_CMD_SET_WIPHY attributes
NL80211_ATTR_WIPHY_FREQ and NL80211_ATTR_WIPHY_SEC_CHAN_OFFSET to allow
userspace to set the operating channel (e.g., hostapd for AP mode).

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 6a1d4ea..6e823cc 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -507,6 +507,9 @@
 
 struct ieee80211_ht_conf {
 	bool enabled;
+	int sec_chan_offset; /* 0 = HT40 disabled; -1 = HT40 enabled, secondary
+			      * channel below primary; 1 = HT40 enabled,
+			      * secondary channel above primary */
 };
 
 /**