qemu: Enable NUMA node tag in pci-root for PPC64

qemu: Enable NUMA node tag in pci-root for PPC64

This patch addresses the same aspects on PPC the bug 1103314 addressed
on x86.

PCI expander bus creates multiple primary PCI busses, where each of these
busses can be assigned a specific NUMA affinity, which, on x86 is
advertised through ACPI on a per-bus basis.

For SPAPR, a PHB's NUMA affinities are assigned on a per-PHB basis, and
there is no mechanism for advertising NUMA affinities to a guest on a
per-bus basis. So, even if qemu-ppc manages to get some sort of multi-bus
topology working using PXB, there is no way to expose the affinities
of these busses to the guest. It can only be exposed on a per-PHB/per-domain
basis.

So patch enables NUMA node tag in pci-root controller on PPC.

The way to set the NUMA node is through the numa_node option of
spapr-pci-host-bridge device. However for the implicit PHB, the only way
to set the numa_node is from the -global option. The -global option applies
to all the PHBs unless explicitly specified with the option on the
respective PHB of CLI. The default PHB has the emulated devices only, so
the patch prevents setting the NUMA node for the default PHB.

Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>