mt7603: main: fix possible NULL pointer dereferencing in mt7603_ampdu…

…_action()

Initialize mt76_txq pointer after ieee80211_txq pointer check.
Remove space after the pointer cast

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>

mt7603_main.c

@@ -456,14 +456,16 @@ mt7603_ampdu_action(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	struct ieee80211_sta *sta = params->sta;
 	struct ieee80211_txq *txq = sta->txq[params->tid];
 	struct mt7603_sta *msta = (struct mt7603_sta *) sta->drv_priv;
-	struct mt76_txq *mtxq = (struct mt76_txq *) txq->drv_priv;
 	u16 tid = params->tid;
 	u16 *ssn = &params->ssn;
 	u8 ba_size = params->buf_size;
+	struct mt76_txq *mtxq;
 
 	if (!txq)
 		return -EINVAL;
 
+	mtxq = (struct mt76_txq *)txq->drv_priv;
+
 	switch (action) {
 	case IEEE80211_AMPDU_RX_START:
 		mt7603_mac_rx_ba_reset(dev, sta->addr, tid);