On the DAMON usage introduction section, the introduction of DAMON
debugfs interface, which is deprecated, is above kernel API, which is
actively supported.  Move the DAMON debugfs intro to bottom, so that
readers have less chances to read it.

Link: https://lkml.kernel.org/r/20230907022929.91361-4-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>