MAINTAINERS: objpool added

objpool, a scalable and lockless ring-array based object pool, was
introduced to replace the original freelist (a LIFO queue based on
singly linked list) to improve kretprobe scalability.

Link: https://lore.kernel.org/all/20231017135654.82270-6-wuqiang.matt@bytedance.com/

Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>