mt76: fix handling ps-poll frames

Hardware station lookup for pspoll frames can fail, which makes the driver
ignore ps-poll frames. Fix the resulting powersave issues by looking up
the station for pspoll frames in software

Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -550,6 +550,12 @@ mt76_check_ps(struct mt76_dev *dev, struct sk_buff *skb)
 	struct mt76_wcid *wcid = status->wcid;
 	bool ps;
 
+	if (ieee80211_is_pspoll(hdr->frame_control) && !wcid) {
+		sta = ieee80211_find_sta_by_ifaddr(dev->hw, hdr->addr2, NULL);
+		if (sta)
+			wcid = status->wcid = (struct mt76_wcid *) sta->drv_priv;
+	}
+
 	if (!wcid || !wcid->sta)
 		return;