[PATCH] USB: Disconnect children when unbinding the hub driver

This patch (as554) makes the hub driver disconnect any child USB devices
when it is unbound from a hub.  Normally this will never happen, but
there are a few oddball ways to unbind the hub driver while leaving the
children intact.  For example, the new "unbind" sysfs attribute can be
used for this purpose.

Given that unbinding hubs with children is now safe, the patch also
removes the code that prevented people from doing so using usbfs.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>