PCI: Assign resources before drivers claim devices (pci_scan_root_bus())

Previously, pci_scan_root_bus() created a root PCI bus, enumerated the
devices on it, and called pci_bus_add_devices(), which made the devices
available for drivers to claim them.

Most callers assigned resources to devices after pci_scan_root_bus()
returns, which may be after drivers have claimed the devices.  This is
incorrect; the PCI core should not change device resources while a driver
is managing the device.

Remove pci_bus_add_devices() from pci_scan_root_bus() and do it after any
resource assignment in the callers.

Note that ARM's pci_common_init_dev() already called pci_bus_add_devices()
after pci_scan_root_bus(), so we only need to remove the first call:

  pci_common_init_dev
    pcibios_init_hw
      pci_scan_root_bus
        pci_bus_add_devices        # first call
    pci_bus_assign_resources
    pci_bus_add_devices            # second call

[bhelgaas: changelog, drop "root_bus" var in alpha common_init_pci(),
return failure earlier in mn10300, add "return" in x86 pcibios_scan_root(),
return early if xtensa platform_pcibios_fixup() fails]
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
CC: Matt Turner <mattst88@gmail.com>
CC: David Howells <dhowells@redhat.com>
CC: Tony Luck <tony.luck@intel.com>
CC: Michal Simek <monstr@monstr.eu>
CC: Ralf Baechle <ralf@linux-mips.org>
CC: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
CC: Sebastian Ott <sebott@linux.vnet.ibm.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Chris Metcalf <cmetcalf@ezchip.com>
CC: Chris Zankel <chris@zankel.net>
CC: Max Filippov <jcmvbkbc@gmail.com>
CC: Thomas Gleixner <tglx@linutronix.de>

arch/tile/kernel/pci.c

@@ -339,6 +339,8 @@ int __init pcibios_init(void)
 			struct pci_bus *next_bus;
 			struct pci_dev *dev;
 
+			pci_bus_add_devices(root_bus);
+
 			list_for_each_entry(dev, &root_bus->devices, bus_list) {
 				/*
 				 * Find the PCI host controller, ie. the 1st

arch/tile/kernel/pci_gx.c

@@ -1030,6 +1030,8 @@ int __init pcibios_init(void)
 alloc_mem_map_failed:
 			break;
 		}
+
+		pci_bus_add_devices(root_bus);
 	}
 
 	return 0;