wifi: mt76: mt7996: Fix mlink lookup in mt7996_tx_prepare_skb

Use proper link_id in mt7996_tx_prepare_skb routine for mlink lookup.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250704-mt7996-mlo-fixes-v1-5-356456c73f43@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>

Author: LorenzoBianconi

drivers/net/wireless/mediatek/mt76/mt7996/mac.c

@@ -1087,9 +1087,9 @@ int mt7996_tx_prepare_skb(struct mt76_dev *mdev, void *txwi_ptr,
 		if (wcid->offchannel)
 			mlink = rcu_dereference(mvif->mt76.offchannel_link);
 		if (!mlink)
-			mlink = &mvif->deflink.mt76;
+			mlink = rcu_dereference(mvif->mt76.link[wcid->link_id]);
 
-		txp->fw.bss_idx = mlink->idx;
+		txp->fw.bss_idx = mlink ? mlink->idx : mvif->deflink.mt76.idx;
 	}
 
 	txp->fw.token = cpu_to_le16(id);