mm/damon/Kconfig: make DAMON_STAT_ENABLED_DEFAULT depend on DAMON_STAT

mm/damon/Kconfig: make DAMON_STAT_ENABLED_DEFAULT depend on DAMON_STAT

The DAMON_STAT_ENABLED_DEFAULT option is strongly tied to DAMON_STAT
option -- enabling it alone is meaningless.  This patch makes
DAMON_STAT_ENABLED_DEFAULT depend on DAMON_STAT, ensuring functional
consistency.

Link: https://lkml.kernel.org/r/20250815092110.811757-1-lienze@kylinos.cn
Fixes: 369c415e6073 ("mm/damon: introduce DAMON_STAT module")
Signed-off-by: Enze Li <lienze@kylinos.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>