MAINTAINERS: update MGLRU entry to reflect current status

We are moving to a far more proactive model of maintainership within mm
and thus put a great deal of emphasis on sub-maintainers being active
within the community both in terms of code contributions and review.

The MGLRU has not had much activity since being added to the kernel and
the current maintainers who kindly stepped up have unfortunately not been
able to contribute a great deal to it for over a year, nor engage all that
heavily in review.

As a result, and within no negative connotations implied whatsoever, it
seems appropriate to downgrade the current maintainers to reviewers.

At this time nobody is quite exercising the maintainer role in this area
of the kernel, but there is encouraging activity from a number of people
who are trusted elsewhere in the kernel, and who have contributed relevant
work or review.

Therefore add further reviewers, and at this stage - to reflect the
reality on the ground - we will not have any sub-maintainers listed at
all.

Each of the files listed are shared with other sections in MAINTAINERS, so
this doesn't reduce sub-maintainer coverage.

Link: https://lore.kernel.org/20260326185629.355476-1-ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: Axel Rasmussen <axelrasmussen@google.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Barry Song <baohua@kernel.org>
Acked-by: SeongJae Park <sj@kernel.org>
Acked-by: Kairui Song <kasong@tencent.com>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Acked-by: Yuanchu Xie <yuanchu@google.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>