md/md-bitmap: Add missing destroy_work_on_stack()

This commit add missed destroy_work_on_stack() operations for
unplug_work.work in bitmap_unplug_async().

Fixes: a022325 ("md/md-bitmap: add a new helper to unplug bitmap asynchrously")
Cc: [email protected]
Signed-off-by: Yuan Can <[email protected]>
Reviewed-by: Yu Kuai <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Song Liu <[email protected]>

Author: Yuan Can

drivers/md/md-bitmap.c

@@ -1285,6 +1285,7 @@ static void bitmap_unplug_async(struct bitmap *bitmap)
 
 	queue_work(md_bitmap_wq, &unplug_work.work);
 	wait_for_completion(&done);
+	destroy_work_on_stack(&unplug_work.work);
 }
 
 static void bitmap_unplug(struct mddev *mddev, bool sync)