net: ethernet: mtk_wed: rename tx_wdma array in rx_wdma

Rename tx_wdma queue array in rx_wdma since this is rx side of wdma soc.
Moreover rename mtk_wed_wdma_ring_setup routine in
mtk_wed_wdma_rx_ring_setup()

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>