tracing/events: Move TRACE_SYSTEM outside of include guard

If TRACE_INCLDUE_FILE is defined, <trace/events/TRACE_INCLUDE_FILE.h>
will be included and compiled, otherwise it will be
<trace/events/TRACE_SYSTEM.h>

So TRACE_SYSTEM should be defined outside of #if proctection,
just like TRACE_INCLUDE_FILE.

Imaging this scenario:

 #include <trace/events/foo.h>
    -> TRACE_SYSTEM == foo
 ...
 #include <trace/events/bar.h>
    -> TRACE_SYSTEM == bar
 ...
 #define CREATE_TRACE_POINTS
 #include <trace/events/foo.h>
    -> TRACE_SYSTEM == bar !!!

and then bar.h will be included and compiled.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A5A9CF1.2010007@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index b0c7ede..1cb0c3aa 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -1,12 +1,12 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM irq
+
 #if !defined(_TRACE_IRQ_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_IRQ_H
 
 #include <linux/tracepoint.h>
 #include <linux/interrupt.h>
 
-#undef TRACE_SYSTEM
-#define TRACE_SYSTEM irq
-
 #define softirq_name(sirq) { sirq##_SOFTIRQ, #sirq }
 #define show_softirq_name(val)			\
 	__print_symbolic(val,			\