cfg80211: remove set but never used variable cf_offset

Perhaps it had been intended to be used, but it clearly isn't.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/chan.c

@@ -464,7 +464,7 @@ bool cfg80211_is_sub_chan(struct cfg80211_chan_def *chandef,
 			  struct ieee80211_channel *chan)
 {
 	int width;
-	u32 cf_offset, freq;
+	u32 freq;
 
 	if (chandef->chan->center_freq == chan->center_freq)
 		return true;
@@ -473,8 +473,6 @@ bool cfg80211_is_sub_chan(struct cfg80211_chan_def *chandef,
 	if (width <= 20)
 		return false;
 
-	cf_offset = width / 2 - 10;
-
 	for (freq = chandef->center_freq1 - width / 2 + 10;
 	     freq <= chandef->center_freq1 + width / 2 - 10; freq += 20) {
 		if (chan->center_freq == freq)