wifi: mt76: dma: do not increment queue head if mt76_dma_add_buf fails

Do not increment queue head if mt76_dma_add_buf fails for Wireless
Ethernet Dispatcher rx queues.

Fixes: cd372b8c ("wifi: mt76: add WED RX support to mt76_dma_{add,get}_buf")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry picked from commit fe13dad8)
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230113105848.34642-1-nbd@nbd.name