perf: Add ifdef to remove unused enum switch warnings

Fix for unused symbols in switch warnings.

Link: http://lkml.kernel.org/r/20120313230302.GA1514@m.redhat.com

Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -144,12 +144,14 @@ struct event_filter;
 enum trace_reg {
 	TRACE_REG_REGISTER,
 	TRACE_REG_UNREGISTER,
+#ifdef CONFIG_PERF_EVENTS
 	TRACE_REG_PERF_REGISTER,
 	TRACE_REG_PERF_UNREGISTER,
 	TRACE_REG_PERF_OPEN,
 	TRACE_REG_PERF_CLOSE,
 	TRACE_REG_PERF_ADD,
 	TRACE_REG_PERF_DEL,
+#endif
 };
 
 struct ftrace_event_call;