sh_eth: use random MAC address if no valid one supplied

On Renesas R-Car based development boards, although a MAC address is printed on
all the Ethernet port labels, U-Boot  doesn't write a valid MAC address  to the
Ether MAHR/MALR registers (there's no storage provided for the Ether MAC address
either), so we have to resort to using a random MAC address...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/sh_eth.c

@@ -2735,6 +2735,11 @@ static int sh_eth_drv_probe(struct platform_device *pdev)
 
 	/* read and set MAC address */
 	read_mac_address(ndev, pd->mac_addr);
+	if (!is_valid_ether_addr(ndev->dev_addr)) {
+		dev_warn(&pdev->dev,
+			 "no valid MAC address supplied, using a random one.\n");
+		eth_hw_addr_random(ndev);
+	}
 
 	/* ioremap the TSU registers */
 	if (mdp->cd->tsu) {