tracing: not necessary to undefine DEFINE_EVENT again

After un-define DEFINE_EVENT in Stage 2, DEFINE_EVENT is not defined to a
specific form. It is not necessary to un-define it again.

Let's skip this.

Link: http://lkml.kernel.org/r/20200612092844.56107-2-richard.weiyang@linux.alibaba.com

Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/trace/trace_events.h

@@ -443,9 +443,6 @@ static struct trace_event_fields trace_event_fields_##call[] = {	\
 	tstruct								\
 	{} };
 
-#undef DEFINE_EVENT
-#define DEFINE_EVENT(template, name, proto, args)
-
 #undef DEFINE_EVENT_PRINT
 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)	\
 	DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
@@ -523,9 +520,6 @@ static inline notrace int trace_event_get_offsets_##call(		\
 	return __data_size;						\
 }
 
-#undef DEFINE_EVENT
-#define DEFINE_EVENT(template, name, proto, args)
-
 #undef DEFINE_EVENT_PRINT
 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)	\
 	DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))