tools/mm: update the usage output to be more organized

Organize the usage options alphabetically and improve the description of
some options.  Also separate the more complicated cull options from the
single use compare options.

Link: https://lkml.kernel.org/r/20231013190350.579407-6-audra@redhat.com


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