mt76: mt76u: use mt76_queue as mt76u_complete_rx context

In order to reuse mt76u_complete_rx for both data and mcu rx queue, rely
on mt76_queue as urb context in mt76u_complete_rx. Moreover set usb rx
endoint according to rx queue in mt76u_submit_rx_buf. This is a
preliminary patch to add mt7663u 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>