mm/fake-numa: handle cases with no SRAT info

Handle more gracefully cases where no SRAT information is available, like
in VMs with no Numa support, and allow fake-numa configuration to complete
successfully in these cases

Link: https://lkml.kernel.org/r/20250127171623.1523171-1-bfaccini@nvidia.com


Fixes: 63db8170 (“mm/fake-numa: allow later numa node hotplug”)
Signed-off-by: Bruno Faccini <bfaccini@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <hyeonggon.yoo@sk.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Len Brown <lenb@kernel.org>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>