Docs/{ABI,admin-guide}/damon: fix various typoes

Docs/{ABI,admin-guide}/damon: fix various typoes

``damon_target_idx`` was wrongly written as ``target_idx`` in the docs.
Fix it all over the place, as well as the wrong directory count, grammar,
etc.

Link: https://lore.kernel.org/20260520012104.93602-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Zenghui Yu <zenghui.yu@linux.dev>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: niecheng <niecheng1@uniontech.com>
Cc: Sakurai Shun <ssh1326@icloud.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>