[PATCH] ppc64: don't create spurious symlinks under node0 sysdev

On partitioned systems we can wind up creating spurious symlinks in
/sys/devices/system/node/node0 to non-present cpus.  The symlinks are
not broken; the problem is that we're potentially misinforming
userspace that there is a relationship between node0 and cpus which
are to be added later.  There's no guarantee at all that a cpu which
is added later will belong to node 0.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>