The wpantund package is only needed for scenarios where the OpenThread
device is operating in network co-processor (NCP) mode. We are not using
NCP, but radio co-processor (RCP instead). The later one works with
ot-br-posix out of the box and we have no need for wpantund, as of now.

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>