Docs/admin-guide/mm/damon/usage: add links to sysfs files hierarchy

Docs/admin-guide/mm/damon/usage: add links to sysfs files hierarchy

'Sysfs Files Hierarchy' section of DAMON usage document shows whole
picture of the interface.  Then sections for detailed explanation of the
files follow.  Due to the amount of the files, navigating between the
whole picture and the section for specific files sometimes require no
subtle amount of scrolling.  Add links from the whole picture to the
dedicated sections for making the navigation easier.

Link: https://lkml.kernel.org/r/20231213190338.54146-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>