mac80211: add comment about reordering

Took me a minute to figure this out, maybe
it's better documented...
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/rx.c

@@ -706,6 +706,8 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
 	/*
 	 * If the current MPDU is in the right order and nothing else
 	 * is stored we can process it directly, no need to buffer it.
+	 * If it is first but there's something stored, we may be able
+	 * to release frames after this one.
 	 */
 	if (mpdu_seq_num == tid_agg_rx->head_seq_num &&
 	    tid_agg_rx->stored_mpdu_num == 0) {