sh_eth: fix TX buffer byte-swapping

commit 3e230993 upstream.

For the little-endian SH771x kernels the driver has to byte-swap the RX/TX
buffers,  however yet unset physcial address from the TX descriptor is used
to call sh_eth_soft_swap(). Use 'skb->data' instead...

Fixes: 31fcb99d ("net: sh_eth: remove __flush_purge_region")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/net/ethernet/renesas/sh_eth.c

@@ -2115,8 +2115,7 @@ static int sh_eth_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	txdesc = &mdp->tx_ring[entry];
 	/* soft swap. */
 	if (!mdp->cd->hw_swap)
-		sh_eth_soft_swap(phys_to_virt(ALIGN(txdesc->addr, 4)),
-				 skb->len + 2);
+		sh_eth_soft_swap(PTR_ALIGN(skb->data, 4), skb->len + 2);
 	txdesc->addr = dma_map_single(&ndev->dev, skb->data, skb->len,
 				      DMA_TO_DEVICE);
 	if (skb->len < ETH_ZLEN)