kho: make sure preservations do not span multiple NUMA nodes

The KHO restoration machinery is not capable of dealing with preservations
that span multiple NUMA nodes. kho_preserve_folio() guarantees the
preservation will only span one NUMA node since folios can't span multiple
nodes.

This leaves kho_preserve_pages(). While semantically kho_preserve_pages()
only deals with 0-order pages, so all preservations should be single page
only, in practice it combines preservations to higher orders for
efficiency. This can result in a preservation spanning multiple nodes.
Break up the preservations into a smaller order if that happens.

Link: https://lkml.kernel.org/r/20260309123410.382308-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>