Docs/admin-guide/mm/damon/reclaim: document statistics parameters

This adds descriptions for the DAMON_RECLAIM statistics parameters.

Link: https://lkml.kernel.org/r/20211210150016.35349-5-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>