Docs/admin-guide/mm/damon/usage: document hugepage_size filter type

This includes both the 'hugepage_size' filter type and the min/max files
used to decide range of sizes to filter on.

Link: https://lkml.kernel.org/r/20250211124437.278873-5-usamaarif642@gmail.com


Signed-off-by: Usama Arif <usamaarif642@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>