usbnet: ipheth: fix risk of NULL pointer deallocation

The cleanup precedure in ipheth_probe will attempt to free a
NULL pointer in dev->ctrl_buf if the memory allocation for
this buffer is not successful. While kfree ignores NULL pointers,
and the existing code is safe, it is a better design to rearrange
the goto labels and avoid this.

Signed-off-by: Georgi Valkov <[e-mail]>
Signed-off-by: Foster Snowhill <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/usb/ipheth.c

···
 	ipheth_free_urbs(dev);
 err_alloc_urbs:
 err_get_macaddr:
-err_alloc_ctrl_buf:
 	kfree(dev->ctrl_buf);
+err_alloc_ctrl_buf:
 err_endpoints:
 	free_netdev(netdev);
 	return retval;