mt76: add memory barrier to DMA queue kick

Ensure that descriptor memory has been fully written before letting the
hardware read it
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/dma.c

@@ -143,6 +143,7 @@ mt76_dma_sync_idx(struct mt76_dev *dev, struct mt76_queue *q)
 static void
 mt76_dma_kick_queue(struct mt76_dev *dev, struct mt76_queue *q)
 {
+	wmb();
 	writel(q->head, &q->regs->cpu_idx);
 }