perf/core: Remove unused local variable

Drop LIST_HEAD() where the variable it declares is never used.

Compiler probably never warned us, because the LIST_HEAD()
initializer is technically 'usage'.

[ mingo: Tweak changelog. ]
Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/1653645835-29206-1-git-send-email-baihaowen@meizu.com

kernel/events/core.c

@@ -4257,7 +4257,6 @@ static void perf_event_remove_on_exec(int ctxn)
 {
 	struct perf_event_context *ctx, *clone_ctx = NULL;
 	struct perf_event *event, *next;
-	LIST_HEAD(free_list);
 	unsigned long flags;
 	bool modified = false;