USB: remove "locktree" routine from the hub driver

This patch (as892) removes the "locktree" routine from the hub driver.
It currently is used in only one place, by a single kernel thread;
hence it isn't doing any good.

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