mm/damon/core: commit damos_quota_goal->nid

DAMOS quota goal uses 'nid' field when the metric is
DAMOS_QUOTA_NODE_MEM_{USED,FREE}_BP.  But the goal commit function is not
updating the goal's nid field.  Fix it.

Link: https://lkml.kernel.org/r/20250719181932.72944-1-sj@kernel.org


Fixes: 0e1c773b ("mm/damon/core: introduce damos quota goal metrics for memory node utilization")	[6.16.x]
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>