mt76: mt7921: add MCU support

Hello Sean Wang,

The patch 1c099ab44727: "mt76: mt7921: add MCU support" from Jan 28, 2021, leads to the following static checker warning:

	drivers/net/wireless/mediatek/mt76/mt7921/mcu.c:409 mt7921_mcu_tx_rate_report()
	error: potentially dereferencing uninitialized 'stats'.

drivers/net/wireless/mediatek/mt76/mt7921/mcu.c
390 static void
391 mt7921_mcu_tx_rate_report(struct mt7921_dev *dev, struct sk_buff *skb,
392 u16 wlan_idx)
393 {
394 struct mt7921_mcu_wlan_info_event *wtbl_info =
395 (struct mt7921_mcu_wlan_info_event *)(skb->data);

   396          struct rate_info rate = {};
   397          u8 curr_idx = wtbl_info->rate_info.rate_idx;
   398          u16 curr = le16_to_cpu(wtbl_info->rate_info.rate[curr_idx]);
   399          struct mt7921_mcu_peer_cap peer = wtbl_info->peer_cap;
   400          struct mt76_phy *mphy = &dev->mphy;
   401          struct mt7921_sta_stats *stats;
   402          struct mt7921_sta *msta;
   403          struct mt76_wcid *wcid;
   404  
   405          if (wlan_idx >= MT76_N_WCIDS)
   406                  return;
   407          wcid = rcu_dereference(dev->mt76.wcid[wlan_idx]);
   408          if (!wcid) {
   409                  stats->tx_rate = rate;
                        ^^^^^^^^^^^^^^^^^^^^^

Not initialized

   410                  return;
   411          }
   412  
   413          msta = container_of(wcid, struct mt7921_sta, wcid);
   414          stats = &msta->stats;
                ^^^^^^^^^^^^^^^^^^^^

   415  
   416          /* current rate */
   417          mt7921_mcu_tx_rate_parse(mphy, &peer, &rate, curr);
   418          stats->tx_rate = rate;
   419  }

regards,
dan carpenter