MAINTAINERS: add section for locking of mm's and VMAs

MAINTAINERS: add section for locking of mm's and VMAs

We place this under memory mapping as related to memory mapping
abstractions in the form of mm_struct and vm_area_struct (VMA).  Now we
have separated out mmap/vma locking logic into the mmap_lock.c and
mmap_lock.h files, so this should encapsulate the majority of the mm
locking logic in the kernel.

Suren is best placed to maintain this logic as the core architect of VMA
locking as a whole.

Link: https://lkml.kernel.org/r/e6ed679a184ca444b20dfa77af96913fd8b5efa0.1744799282.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>