thunderbolt: Mark XDomain as unplugged when router is removed

In the Linux kernel, the following vulnerability has been resolved:

thunderbolt: Mark XDomain as unplugged when router is removed

I noticed that when we do discrete host router NVM upgrade and it gets

hot-removed from the PCIe side as a result of NVM firmware authentication,

if there is another host connected with enabled paths we hang in tearing

them down. This is due to fact that the Thunderbolt networking driver

also tries to cleanup the paths and ends up blocking in

tb_disconnect_xdomain_paths() waiting for the domain lock.

However, at this point we already cleaned the paths in tb_stop() so

there is really no need for tb_disconnect_xdomain_paths() to do that

anymore. Furthermore it already checks if the XDomain is unplugged and

bails out early so take advantage of that and mark the XDomain as

unplugged when we remove the parent router.