mt76: mt7915: fix memleak when mt7915_unregister_device()

mt7915_tx_token_put() should get call before mt76_free_pending_txwi().

Fixes: f285dfb9

 ("mt76: mt7915: reset token when mac_reset happens")
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>