USB: set hub's default autosuspend delay as 0

This patch sets hub device's default autosuspend delay as 0 to
speedup bus suspend, see comments in code for details.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>