mt76: mt7915: cleanup mcu tx queue in mt7915_dma_reset()

Cleanup mcu queues in mt7915_mac_reset_work().

Fixes: e637763b ("mt76: move mcu queues to mt76_dev q_mcu array")
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>