Add function setup_numa_memblock() for setting up a memory layout with
multiple NUMA nodes in a previously allocated dummy physical memory.
This function can be used in place of setup_memblock() in tests that need
to simulate a NUMA system.

setup_numa_memblock():
- allows for setting up a memory layout by specifying the fraction of
  MEM_SIZE in each node

Set CONFIG_NODES_SHIFT to 4 when building with NUMA=1 to allow for up to
16 NUMA nodes.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Rebecca Mckeever <remckee0@gmail.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/4566d816a85f009268d4858d1ef06c7571a960f9.1663046060.git.remckee0@gmail.com