PCI: Refactor pci_bus_assign_domain_nr() for CONFIG_PCI_DOMAINS_GENERIC

Instead of assigning bus->domain_nr inside pci_bus_assign_domain_nr(),
return the domain and let the caller do the assignment.  Rename
pci_bus_assign_domain_nr() to pci_bus_find_domain_nr() to reflect this.

No functional change intended.

[bhelgaas: changelog]
Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8e3ef72..380d46d 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2127,7 +2127,9 @@
 	b->sysdata = sysdata;
 	b->ops = ops;
 	b->number = b->busn_res.start = bus;
-	pci_bus_assign_domain_nr(b, parent);
+#ifdef CONFIG_PCI_DOMAINS_GENERIC
+	b->domain_nr = pci_bus_find_domain_nr(b, parent);
+#endif
 	b2 = pci_find_bus(pci_domain_nr(b), bus);
 	if (b2) {
 		/* If we already got to this bus through a different bridge, ignore it */