[PATCH] x86-64: Don't enable NUMA for a single node in K8 NUMA scanning

This was supposed to see the full memory on a ASUS A8SX motherboard
with 4GB RAM where the northbridge reports less memory, but it didn't
help there. But it's a reasonable change so let's include it anyways.

Signed-off-by: Andi Kleen <ak@suse.de>