net: ethernet: ti: cpsw-phy-sel: check bus_find_device() ret value

This fixes klockworks warnings: Pointer 'dev' returned from call to
function 'bus_find_device' at line 179 may be NULL and will be dereferenced
at line 181.

    cpsw-phy-sel.c:179: 'dev' is assigned the return value from function 'bus_find_device'.
    bus.c:342: 'bus_find_device' explicitly returns a NULL value.
    cpsw-phy-sel.c:181: 'dev' is dereferenced by passing argument 1 to function 'dev_get_drvdata'.
    device.h:1024: 'dev' is passed to function 'dev_get_drvdata'.
    device.h:1026: 'dev' is explicitly dereferenced.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
[nsekhar@ti.com: add an error message, fix return path]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/cpsw-phy-sel.c

@@ -177,12 +177,18 @@ void cpsw_phy_sel(struct device *dev, phy_interface_t phy_mode, int slave)
 	}
 
 	dev = bus_find_device(&platform_bus_type, NULL, node, match);
-	of_node_put(node);
+	if (!dev) {
+		dev_err(dev, "unable to find platform device for %pOF\n", node);
+		goto out;
+	}
+
 	priv = dev_get_drvdata(dev);
 
 	priv->cpsw_phy_sel(priv, phy_mode, slave);
 
 	put_device(dev);
+out:
+	of_node_put(node);
 }
 EXPORT_SYMBOL_GPL(cpsw_phy_sel);