net: ethernet: ti: cpsw: fix secondary-emac probe error path

commit a7fe9d46 upstream.

Make sure to deregister the primary device in case the secondary emac
fails to probe.

kernel BUG at /home/johan/work/omicron/src/linux/net/core/dev.c:7743!
...
[<c05b3dec>] (free_netdev) from [<c04fe6c0>] (cpsw_probe+0x9cc/0xe50)
[<c04fe6c0>] (cpsw_probe) from [<c047b28c>] (platform_drv_probe+0x5c/0xc0)

Fixes: d9ba8f9e ("driver: net: ethernet: cpsw: dual emac interface
implementation")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/ethernet/ti/cpsw.c

@@ -2279,7 +2279,7 @@ static int cpsw_probe(struct platform_device *pdev)
 		ret = cpsw_probe_dual_emac(pdev, priv);
 		if (ret) {
 			cpsw_err(priv, probe, "error probe slave 2 emac interface\n");
-			goto clean_ale_ret;
+			goto clean_unregister_netdev_ret;
 		}
 	}
 
@@ -2287,6 +2287,8 @@ static int cpsw_probe(struct platform_device *pdev)
 
 	return 0;
 
+clean_unregister_netdev_ret:
+	unregister_netdev(ndev);
 clean_ale_ret:
 	cpsw_ale_destroy(priv->ale);
 clean_dma_ret: