lack of ->remove in 9p virtio driver

Hi Eric,

    Just cleaning up patches for 2.6.25 merge, and noticed that 
net/9p/trans_virtio.c doesn't have a remove function.  This will crash when 
removing the module (console doesn't have one because it can't really be 
removed).

    I'll push the latest queue in a couple of hours: the most important thing 
is that it's now drivers' responsibility to call (the new!) 
vdev->config->reset() function on shutdown.

Cheers,
Rusty.