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/sta_info.c b/net/mac80211/sta_info.c
index c426504..5a11078 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -899,7 +899,8 @@
 	struct ieee80211_local *local = sdata->local;
 	int sent, buffered;
 
-	drv_sta_notify(local, sdata, STA_NOTIFY_AWAKE, &sta->sta);
+	if (!(local->hw.flags & IEEE80211_HW_AP_LINK_PS))
+		drv_sta_notify(local, sdata, STA_NOTIFY_AWAKE, &sta->sta);
 
 	if (!skb_queue_empty(&sta->ps_tx_buf))
 		sta_info_clear_tim_bit(sta);