mm/damon/reclaim: reset enabled when DAMON start failed

When the startup fails, 'enabled' parameter is not reset.  As a result,
users show the parameter 'Y' while it is not really working.  Fix it by
resetting 'enabled' to 'false' when the work is failed.

Link: https://lkml.kernel.org/r/20250706193207.39810-5-sj@kernel.org


Fixes: 04e98764 ("mm/damon/reclaim: enable and disable synchronously")
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>