x86/PCI: set_pci_bus_resources_arch_default cleanups

Rename set_pci_bus_resources_arch_default to x86_pci_root_bus_res_quirks, move
the weak version from common.c to i386.c, and before calling, make sure it's a
root bus.

Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
index f1817f7..a85bef2 100644
--- a/arch/x86/pci/i386.c
+++ b/arch/x86/pci/i386.c
@@ -238,6 +238,10 @@
  */
 fs_initcall(pcibios_assign_resources);
 
+void __weak x86_pci_root_bus_res_quirks(struct pci_bus *b)
+{
+}
+
 /*
  *  If we set up a device for bus mastering, we need to check the latency
  *  timer as certain crappy BIOSes forget to set it properly.