Use mutex to protect global acpi_pci_drivers list against PCI
host bridge hotplug operations.
Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NTaku Izumi <izumi.taku@jp.fujitsu.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>