wifi: mt76: mt7915: fix list corruption after hardware restart

In the Linux kernel, the following vulnerability has been resolved:

wifi: mt76: mt7915: fix list corruption after hardware restart

Since stations are recreated from scratch, all lists that wcids are added to must be cleared before calling ieee80211_restart_hw. Set wcid->sta = 0 for each wcid entry in order to ensure that they are not added again before they are ready.