wifi: mt76: mt7996: clear stale link state on full reset

After a full chip reset, mac80211 reconfig replays interface, link and
channel context setup. mt7996_vif_link_add() short-circuits when the
link_id is still marked in mvif->valid_links, a state introduced for
postponing link teardown to interface removal. The reset path frees the
link structures without clearing those bits, so the replayed setup never
re-creates dev_info/bss_info/STA records in the restarted firmware and
never re-registers the link wcid, leaving the device inoperative.

The reset path also leaks every allocated MLD index: per-link indices
and the per-vif group/remap indices are re-allocated from scratch during
reconfig, but the old bits stay set in the masks, so repeated full
resets exhaust the index space.

Clear valid_links in the reset vif iterator and reset the MLD index
masks alongside the existing omac_mask clearing.

Fixes: ace5d3b ("wifi: mt76: mt7996: improve hardware restart reliability")
Fixes: 0881370 ("wifi: mt76: mt7996: Destroy vif active links in mt7996_remove_interface()")
Link: https://patch.msgid.link/20260724124813.3961474-26-nbd@nbd.name
Signed-off-by: Felix Fietkau <nbd@nbd.name>

Author: nbd168

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

@@ -2449,6 +2449,7 @@ mt7996_mac_reset_vif_iter(void *data, u8 *mac, struct ieee80211_vif *vif)
 		rcu_assign_pointer(mvif->link[i], NULL);
 		kfree_rcu(mlink, rcu_head);
 	}
+	mvif->valid_links = 0;
 	rcu_read_unlock();
 }
 
@@ -2483,6 +2484,8 @@ mt7996_mac_full_reset(struct mt7996_dev *dev)
 
 	mt7996_for_each_phy(dev, phy)
 		phy->omac_mask = 0;
+	dev->mld_idx_mask = 0;
+	dev->mld_remap_idx_mask = 0;
 
 	ieee80211_iterate_stations_atomic(hw, mt7996_mac_reset_sta_iter, dev);
 	mt76_reset_device(&dev->mt76);