Docs/ABI/damon: document effective_bytes sysfs file

Update the DAMON ABI doc for the effective_bytes sysfs file and the
kdamond state file input command for updating the content of the file.

Link: https://lkml.kernel.org/r/20240219194431.159606-5-sj@kernel.org


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