mt76: dma: introduce mt76_dma_queue_reset routine

Introduce mt76_dma_queue_reset utility routine to reset a given hw
queue. This is a preliminary patch to introduce mt7921 chip reset
support.

Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>