powerpc/PCI: allow reallocation on PA Semi

We believe there's no reason to prevent reallocation on PA Semi, so
revert to the default of "allow reallocation if necessary."

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: linuxppc-dev@lists.ozlabs.org
Tested-by: Olof Johansson <olof@lixom.net>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>