mt76: mt7615: use ieee80211_free_txskb() in mt7615_tx_token_put()

We should use ieee80211_free_txskb() to report skb status avoid wrong
aql accounting after reset.

Cc: stable@vger.kernel.org
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>