arm64: PCI: Restructure pcibios_root_bridge_prepare()

Restructure the pcibios_root_bridge_prepare() as the preparation for
supporting cases when no real ACPI device is related to the PCI host
bridge.

No functional change.

Link: https://lore.kernel.org/r/20210726180657.142727-4-boqun.feng@gmail.com
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/pci.c

@@ -82,14 +82,19 @@ int acpi_pci_bus_find_domain_nr(struct pci_bus *bus)
 
 int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
 {
-	if (!acpi_disabled) {
-		struct pci_config_window *cfg = bridge->bus->sysdata;
-		struct acpi_device *adev = to_acpi_device(cfg->parent);
-		struct device *bus_dev = &bridge->bus->dev;
+	struct pci_config_window *cfg;
+	struct acpi_device *adev;
+	struct device *bus_dev;
 
-		ACPI_COMPANION_SET(&bridge->dev, adev);
-		set_dev_node(bus_dev, acpi_get_node(acpi_device_handle(adev)));
-	}
+	if (acpi_disabled)
+		return 0;
+
+	cfg = bridge->bus->sysdata;
+	adev = to_acpi_device(cfg->parent);
+	bus_dev = &bridge->bus->dev;
+
+	ACPI_COMPANION_SET(&bridge->dev, adev);
+	set_dev_node(bus_dev, acpi_get_node(acpi_device_handle(adev)));
 
 	return 0;
 }