PCI/ACPI: Reserve firmware-allocated resources for hot-added root buses

Firmware may have assigned PCI BARs for hot-added devices, so reserve
those resources before trying to allocate more.

[bhelgaas: move empty weak definition here]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index ad6a8b6..847f3ca 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -158,6 +158,8 @@
 	return ret;
 }
 
+void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }
+
 /**
  * pci_bus_add_device - add a single device
  * @dev: device to add