powerpc/pci: Fold pcibios_setup_device() into pcibios_bus_add_device()

pcibios_bus_add_device() is the only caller of pcibios_setup_device().
Fold them together since there's no real reason to keep them separate.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200110070207.439-2-oohall@gmail.com