MAINTAINERS: add stray rmap file to mm rmap section

MAINTAINERS: add stray rmap file to mm rmap section

page_vma_mapped_walk() is used to traverse page tables from a VMA, used by
rmap logic once the reverse mapping has been traversed to the VMA level.

It is also used by other users (migration, damon, etc.) but is primarily
used by the reverse mapping and is a key part of its logic, so it seems
appropriate to place it here.

Link: https://lkml.kernel.org/r/20250617165142.173716-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>