mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()

mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()

Commit c0cb9d91bf297 ("mm/damon/paddr: report filter-passed bytes back for
DAMOS_STAT action") added unused variable in damon_pa_stat(), due to a
copy-and-paste error.  Remove it.

Link: https://lkml.kernel.org/r/20250513002715.40126-4-sj@kernel.org
Fixes: c0cb9d91bf29 ("mm/damon/paddr: report filter-passed bytes back for DAMOS_STAT action")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>