powerpc/pci: Don't unset PCI resources for VFs

Flag PCI_REASSIGN_ALL_RSRC is used to ignore resources information setup by
firmware, so that kernel would re-assign all resources of pci devices.

On powerpc arch, this happens in a header fixup function
pcibios_fixup_resources(), which will clean up the resources if this flag
is set. This works fine for PFs, since after clean up, kernel will
re-assign the resources in pcibios_resource_survey().

Below is a simple call flow on how it works:

    pcibios_init
      pcibios_scan_phb
        pci_scan_child_bus
          ...
            pci_device_add
              pci_fixup_device(pci_fixup_header)
                pcibios_fixup_resources                     # header fixup
                  for (i = 0; i < DEVICE_COUNT_RESOURCE; i++)
                    dev->resource[i].start = 0
      pcibios_resource_survey                               # re-assign
        pcibios_allocate_resources

However, the VF resources won't be re-assigned, since the VF resources are
completely determined by the PF resources, and the PF resources have
already been reassigned. This means we need to leave VF's resources
un-cleared in pcibios_fixup_resources().

In this patch, we skip the resource unset process in
pcibios_fixup_resources(), if the pci_dev is a VF.
Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/pci-common.c

@@ -788,6 +788,10 @@ static void pcibios_fixup_resources(struct pci_dev *dev)
 		       pci_name(dev));
 		return;
 	}
+
+	if (dev->is_virtfn)
+		return;
+
 	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
 		struct resource *res = dev->resource + i;
 		struct pci_bus_region reg;