mac80211: add HW flag for disabling auto link-PS in AP mode

When operating in AP mode the wl1271 hardware filters out null-data
packets as well as management packets. This makes it impossible for
mac80211 to monitor the PS mode by using the PM bit of incoming frames.

Implement a HW flag to indicate that mac80211 should ignore the PM bit.
In addition, expose ieee80211_sta_ps_transition() to make low-level
drivers capable of controlling PS-mode.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/status.c b/net/mac80211/status.c
index 38a7972..ffb0de9 100644
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -98,6 +98,10 @@
 	 *  (b) always process RX events before TX status events if ordering
 	 *      can be unknown, for example with different interrupt status
 	 *	bits.
+	 *  (c) if PS mode transitions are manual (i.e. the flag
+	 *      %IEEE80211_HW_AP_LINK_PS is set), always process PS state
+	 *      changes before calling TX status events if ordering can be
+	 *	unknown.
 	 */
 	if (test_sta_flags(sta, WLAN_STA_PS_STA) &&
 	    skb_queue_len(&sta->tx_filtered) < STA_MAX_TX_BUFFER) {