powerpc/pci: Remove pcibios_do_bus_setup()

The function pcibios_do_bus_setup() was used by pcibios_fixup_bus()
to perform setup that is different between the 32-bit and 64-bit
code.  This difference no longer exists, thus the function is removed
and the setup now done directly from pci-common.c.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>