PCI: acpiphp: Stop disabling bridges on remove

acpiphp_disable_slot() turns off power to the slot immediately after
calling disable_device(), so there's no point in disabling any bridges
below the slot: we're about to turn them off anyway.

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