mac80211: use kfree_skb() instead of kfree()

sk_buff structs should be freed using kfree_skb().

This was introduced recently in 02945821 "mac80211: Save probe
response data for bss".
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/iface.c

@@ -474,7 +474,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 		RCU_INIT_POINTER(sdata->u.ap.probe_resp, NULL);
 		synchronize_rcu();
 		kfree(old_beacon);
-		kfree(old_probe_resp);
+		kfree_skb(old_probe_resp);
 
 		/* down all dependent devices, that is VLANs */
 		list_for_each_entry_safe(vlan, tmpsdata, &sdata->u.ap.vlans,