mt76: usb: fix use of q->head and q->tail

Their use is reversed compared to DMA. The order for DMA makes more sense,
so let's use that

Signed-off-by: Felix Fietkau <nbd@nbd.name>
This commit is contained in:
Felix Fietkau 2020-08-23 12:42:18 +02:00
commit 95f61e17ef