Change CONFIG_PER_VMA_LOCK_STATS to be disabled by default, as most users
don't need it.  Add configuration help to clarify its usage.

Link: https://lkml.kernel.org/r/20230428173533.18158-1-surenb@google.com
Fixes: 52f23865 ("mm: introduce per-VMA lock statistics")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>