MAINTAINERS: add Chengming Zhou as a zswap reviewer

MAINTAINERS: add Chengming Zhou as a zswap reviewer

I have been actively contributing to zswap and reviewing zswap patches for
a while, and I am already getting CC'd on most of them.  So add myself as
a reviewer, will continue to work on it and help with the review process.

Link: https://lkml.kernel.org/r/20240220073851.865113-1-chengming.zhou@linux.dev
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>