mac80211: remove unused function

Remove the unused function is_ieee80211_device().
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -175,12 +175,6 @@ static __le16 ieee80211_duration(struct ieee80211_tx_data *tx,
 	return cpu_to_le16(dur);
 }
 
-static inline int is_ieee80211_device(struct ieee80211_local *local,
-				      struct net_device *dev)
-{
-	return local == wdev_priv(dev->ieee80211_ptr);
-}
-
 /* tx handlers */
 static ieee80211_tx_result debug_noinline
 ieee80211_tx_h_dynamic_ps(struct ieee80211_tx_data *tx)