net: ethernet: mtk_wed: setup WDMA_RING_TX(0) for non-DBDC MT7986

WDMA_RING_TX(0) is required to set MTK_WED_WDMA_RING_TX for WED RX
but on a non-DBDC MT7986 it is never setup because idx is 1.

Setting MTK_WED_WDMA_RING_TX with WDMA_RING_TX(1) is not feasible because
WED still tries to send through WDMA_RING_TX(0). This is verified with
register dump.

Fix this by calling mtk_wed_wdma_tx_ring_setup if wed is v2 and
rx_ring[0] is not allocated and reset tx_wdma[0] if it's already
allocated also add error messages and bail when mtk_wed_start fails.

Fixes: 4c5de09eb0d0 ("net: ethernet: mtk_wed: add configure wed wo support")
Signed-off-by: Zhi-Jun You <hujy652@gmail.com>
Link: https://patch.msgid.link/20261026-wedfix-v6-4-a52f6b15d2fc@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>