Use pci_stop_and_remove_bus_device() like most other hotplug drivers
rather than the special-purpose "behind_bridge" variant.  This just
means we have to iterate through all the devices downstream of the
bridge ourselves, which is the same thing pci_stop_behind_bridge()
did.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>