tools/mm: remove references to free_ts from page_owner_sort

With the removal of free timestamps from page_owner output, we no longer
need to handle this case or the "unreleased" case.  Remove all references
to both cases.

Link: https://lkml.kernel.org/r/20231013190350.579407-3-audra@redhat.com


Signed-off-by: Audra Mitchell <audra@redhat.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Georgi Djakov <djakov@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>