PCI: Don't auto-realloc if we're preserving firmware config

Prevent auto-enabling of bridges reallocation when the FW tells us that the
initial configuration must be preserved for a given host bridge.

Link: https://lore.kernel.org/r/20190615002359.29577-3-benh@kernel.crashing.orgSigned-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/setup-bus.c

@@ -1684,10 +1684,15 @@ static enum enable_type pci_realloc_detect(struct pci_bus *bus,
 					   enum enable_type enable_local)
 {
 	bool unassigned = false;
+	struct pci_host_bridge *host;
 
 	if (enable_local != undefined)
 		return enable_local;
 
+	host = pci_find_host_bridge(bus);
+	if (host->preserve_config)
+		return auto_disabled;
+
 	pci_walk_bus(bus, iov_resources_unassigned, &unassigned);
 	if (unassigned)
 		return auto_enabled;