tracing: Fix memory leak on instance deletion

When an instance is created, it also gets a snapshot ring buffer
allocated (with minimum of pages). But when it is deleted the snapshot
buffer is not. There was a helper function added to match the allocation
of these ring buffers to a way to free them, but it wasn't used by
the deletion of an instance. Using that helper function solves this
memory leak.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -6349,8 +6349,7 @@ static int instance_delete(const char *name)
 	event_trace_del_tracer(tr);
 	ftrace_destroy_function_files(tr);
 	debugfs_remove_recursive(tr->dir);
-	free_percpu(tr->trace_buffer.data);
-	ring_buffer_free(tr->trace_buffer.buffer);
+	free_trace_buffers(tr);
 
 	kfree(tr->name);
 	kfree(tr);