[PATCH] powerpc numa: Support sparse online node map

[PATCH] powerpc numa: Support sparse online node map

The powerpc numa code unconditionally onlines all nodes from 0 to the
highest node id found, regardless of whether cpus or memory are
present in the nodes.  This wastes 8K per node and complicates some
cpu and memory hotplug situations, such as adding a resource that
doesn't map to one of the nodes discovered at boot.

Set nodes online as resources are scanned.  Fall back to node 0 only
when we're sure this isn't a NUMA machine.

Instead of defaulting to node 0 for cases of hot-adding a resource
which doesn't belong to any initialized node, assign it to the first
online node.

Signed-off-by: Nathan Lynch <nathanl@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>