mt76: mt7615: remove mtxq->agg_ssn assignment

It is not used anywhere for this driver
Signed-off-by: NFelix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7615/main.c

@@ -818,7 +818,6 @@ mt7615_ampdu_action(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	case IEEE80211_AMPDU_TX_START:
 		ssn = mt7615_mac_get_sta_tid_sn(dev, msta->wcid.idx, tid);
 		params->ssn = ssn;
-		mtxq->agg_ssn = IEEE80211_SN_TO_SEQ(ssn);
 		ret = IEEE80211_AMPDU_TX_START_IMMEDIATE;
 		break;
 	case IEEE80211_AMPDU_TX_STOP_CONT: