PCI: Add a generic weak pcibios_fixup_bus()

Multiple architectures define this as an empty function, and I'm adding
another one as part of the RISC-V port.  Add a __weak version of
pcibios_fixup_bus() and delete the now-obselete ones in a handful of
ports.

The only functional change should be that microblaze used to export
pcibios_fixup_bus().  None of the other architectures exports this, so I
just dropped it.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/probe.c

@@ -2288,6 +2288,15 @@ void pcie_bus_configure_settings(struct pci_bus *bus)
 }
 EXPORT_SYMBOL_GPL(pcie_bus_configure_settings);
 
+/*
+ * Called after each bus is probed, but before its children are examined.  This
+ * is marked as __weak because multiple architectures define it.
+ */
+void __weak pcibios_fixup_bus(struct pci_bus *bus)
+{
+       /* nothing to do, expected to be removed in the future */
+}
+
 unsigned int pci_scan_child_bus(struct pci_bus *bus)
 {
 	unsigned int devfn, pass, max = bus->busn_res.start;