perf/events/core: Drop unused variable after cleanup

... in 3a497f48 ("perf: Simplify perf_event_exit_task_context()")
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1399720259-28275-1-git-send-email-bp@alien8.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/events/core.c

@@ -7431,7 +7431,7 @@ __perf_event_exit_task(struct perf_event *child_event,
 
 static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
 {
-	struct perf_event *child_event, *tmp;
+	struct perf_event *child_event;
 	struct perf_event_context *child_ctx;
 	unsigned long flags;