x86/PCI: Refine PCI support check in pcibios_init()

Also consider raw_pci_ext_ops when validating if a system has PCI support.
This leads to proper resource allocation via pcibios_resource_survey() in
the case where PCI config space is exclusively accessed through MMCONFIG.
Signed-off-by: NAdrian-Ken Rueegsegger <ken@codelabs.ch>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

arch/x86/pci/common.c

@@ -516,7 +516,7 @@ void __init pcibios_set_cache_line_size(void)
 
 int __init pcibios_init(void)
 {
-	if (!raw_pci_ops) {
+	if (!raw_pci_ops && !raw_pci_ext_ops) {
 		printk(KERN_WARNING "PCI: System does not support PCI\n");
 		return 0;
 	}