via-rhine: dma_wmb transmit barrier.

Follow the now usual transmit descriptor update path:
1. content change
2. dma_wmb
3. ownership change

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/via/via-rhine.c b/drivers/net/ethernet/via/via-rhine.c
index 8195fcd..86ca8b2 100644
--- a/drivers/net/ethernet/via/via-rhine.c
+++ b/drivers/net/ethernet/via/via-rhine.c
@@ -1849,7 +1849,7 @@
 
 	netdev_sent_queue(dev, skb->len);
 	/* lock eth irq */
-	wmb();
+	dma_wmb();
 	rp->tx_ring[entry].tx_status |= cpu_to_le32(DescOwn);
 	wmb();