net: mv643xx_eth: do not use port number as platform device id

The port number is only local to the ethernet block, not global, so
there can be two ethernet blocks both using the same port, like
kirkwood with both using port 0.

Fix this by using the array index offset for the allocated platform
devices as the id.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mv643xx_eth.c

@@ -2483,6 +2483,7 @@ static int mv643xx_eth_shared_of_add_port(struct platform_device *pdev,
 	struct resource res;
 	const char *mac_addr;
 	int ret;
+	int dev_num = 0;
 
 	memset(&ppd, 0, sizeof(ppd));
 	ppd.shared = pdev;
@@ -2503,6 +2504,14 @@ static int mv643xx_eth_shared_of_add_port(struct platform_device *pdev,
 		return -EINVAL;
 	}
 
+	while (dev_num < 3 && port_platdev[dev_num])
+		dev_num++;
+
+	if (dev_num == 3) {
+		dev_err(&pdev->dev, "too many ports registered\n");
+		return -EINVAL;
+	}
+
 	mac_addr = of_get_mac_address(pnp);
 	if (mac_addr)
 		memcpy(ppd.mac_addr, mac_addr, 6);
@@ -2521,7 +2530,7 @@ static int mv643xx_eth_shared_of_add_port(struct platform_device *pdev,
 		of_property_read_u32(pnp, "duplex", &ppd.duplex);
 	}
 
-	ppdev = platform_device_alloc(MV643XX_ETH_NAME, ppd.port_number);
+	ppdev = platform_device_alloc(MV643XX_ETH_NAME, dev_num);
 	if (!ppdev)
 		return -ENOMEM;
 	ppdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
@@ -2538,7 +2547,7 @@ static int mv643xx_eth_shared_of_add_port(struct platform_device *pdev,
 	if (ret)
 		goto port_err;
 
-	port_platdev[ppd.port_number] = ppdev;
+	port_platdev[dev_num] = ppdev;
 
 	return 0;