mac80211: Fix (dynamic) power save entry

Currently hardware with !IEEE80211_HW_PS_NULLFUNC_STACK and
IEEE80211_HW_REPORTS_TX_ACK_STATUS will never enter PSM due to the
conditions in the power save entry functions.

Fix those conditions.
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -436,10 +436,12 @@ static void ieee80211_enable_ps(struct ieee80211_local *local,
 		if (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK)
 			ieee80211_send_nullfunc(local, sdata, 1);
 
-		if (!(local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS)) {
-			conf->flags |= IEEE80211_CONF_PS;
-			ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
-		}
+		if ((local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) &&
+		    (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS))
+			return;
+
+		conf->flags |= IEEE80211_CONF_PS;
+		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 	}
 }
 
@@ -558,7 +560,8 @@ void ieee80211_dynamic_ps_enable_work(struct work_struct *work)
 	    (!(ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED)))
 		ieee80211_send_nullfunc(local, sdata, 1);
 
-	if (!(local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) ||
+	if (!((local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) &&
+	      (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK)) ||
 	    (ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED)) {
 		ifmgd->flags &= ~IEEE80211_STA_NULLFUNC_ACKED;
 		local->hw.conf.flags |= IEEE80211_CONF_PS;