tracing/filters: don't remove old filters when failed to write subsys->filter

If writing subsys->filter returns EINVAL or ENOSPC, the original
filters in subsys/ and subsys/events/ will be removed. This is
definitely wrong.

[ Impact: fix filter setting semantics on error condition ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49ED8DD2.2070700@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_events.c

@@ -600,7 +600,6 @@ subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
 
 	err = filter_add_subsystem_pred(system, pred);
 	if (err < 0) {
-		filter_free_subsystem_preds(system);
 		filter_free_pred(pred);
 		return err;
 	}