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>

arch/sparc/kernel/pci.c

@@ -690,10 +690,6 @@ struct pci_bus *pci_scan_one_pbm(struct pci_pbm_info *pbm,
 	return bus;
 }
 
-void pcibios_fixup_bus(struct pci_bus *pbus)
-{
-}
-
 resource_size_t pcibios_align_resource(void *data, const struct resource *res,
 				resource_size_t size, resource_size_t align)
 {