mac80211: fix memory leak in ieee80211_send_probe_req

This patch fixes memory leak in ieee80211_send_probe_req, which
is introduced in 7c12ce8b:

	mac80211: use Probe Request template when sending a direct scan

The patch is against the latest wireless-test tree.
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Reviewed-by: NKalle Valo <kalle.valo@nokia.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/util.c

@@ -1028,6 +1028,7 @@ void ieee80211_send_probe_req(struct ieee80211_sub_if_data *sdata, u8 *dst,
 
 	IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
 	ieee80211_tx_skb(sdata, skb);
+	kfree(buf);
 }
 
 u32 ieee80211_sta_get_rates(struct ieee80211_local *local,