vl.c: Don't limit node count by smp count

[I've sent this patch couple of months ago and noticed it
 didn't make it's way in - so I'm sending it again]

It is possible to create CPU-less NUMA nodes, node amount shouldn't be
limited by amount of CPUs.

Tested-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Acked-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
