PCI: acpiphp: Add is_hotplug_bridge detection

PCI: acpiphp: Add is_hotplug_bridge detection

When system support hotplug bridge with children hotplug slots, we need
to make sure that parent bridge get preallocated resource so later when
device is plugged into children slot, those children devices will get
resource allocated.

We do not meet this problem, because for PCIe hotplug card, when acpiphp
is used, pci_scan_bridge will set that for us when detect hotplug bit in
slot cap.

Reported-and-tested-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>