PCI/ACPI: provide MMCONFIG address for PCI host bridges

This patch provide MMCONFIG address for PCI host bridges, which will
be used to support host bridge hotplug.  It gets MMCONFIG address
by evaluating _CBA method if available.

Reviewed-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jiang Liu <liuj97@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 7aff631..ec54014c 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -505,6 +505,8 @@
 	strcpy(acpi_device_class(device), ACPI_PCI_ROOT_CLASS);
 	device->driver_data = root;
 
+	root->mcfg_addr = acpi_pci_root_get_mcfg_addr(device->handle);
+
 	/*
 	 * All supported architectures that use ACPI have support for
 	 * PCI domains, so we indicate this in _OSC support capabilities.