tracing: Make unregister_trigger() static

Nothing uses unregister_trigger() outside of trace_events_trigger.c file,
thus it should be static. Not sure why this was ever converted, because
its counter part, register_trigger(), was always static.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.h

@@ -1533,9 +1533,6 @@ extern int event_trigger_init(struct event_trigger_ops *ops,
 extern int trace_event_trigger_enable_disable(struct trace_event_file *file,
 					      int trigger_enable);
 extern void update_cond_flag(struct trace_event_file *file);
-extern void unregister_trigger(char *glob, struct event_trigger_ops *ops,
-			       struct event_trigger_data *test,
-			       struct trace_event_file *file);
 extern int set_trigger_filter(char *filter_str,
 			      struct event_trigger_data *trigger_data,
 			      struct trace_event_file *file);

kernel/trace/trace_events_trigger.c

@@ -579,7 +579,7 @@ static int register_trigger(char *glob, struct event_trigger_ops *ops,
  * Usually used directly as the @unreg method in event command
  * implementations.
  */
-void unregister_trigger(char *glob, struct event_trigger_ops *ops,
+static void unregister_trigger(char *glob, struct event_trigger_ops *ops,
 			       struct event_trigger_data *test,
 			       struct trace_event_file *file)
 {