s() to stop/remove pci root bus.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: Len Brown <lenb@kernel.org>
CC: linux-acpi@vger.kernel.org