tracing: Annotate event field-defining functions with __init

Those functions are called either during kernel boot or module init.

Before:

$ dmesg | grep 'Freeing unused kernel memory'
Freeing unused kernel memory: 1208k freed
Freeing unused kernel memory: 1360k freed
Freeing unused kernel memory: 1960k freed

After:

$ dmesg | grep 'Freeing unused kernel memory'
Freeing unused kernel memory: 1236k freed
Freeing unused kernel memory: 1388k freed
Freeing unused kernel memory: 1960k freed

Link: http://lkml.kernel.org/r/5125877D.5000201@huawei.com

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/trace/ftrace.h

@@ -324,7 +324,7 @@ static struct trace_event_functions ftrace_event_type_funcs_##call = {	\
 
 #undef DECLARE_EVENT_CLASS
 #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, func, print)	\
-static int notrace							\
+static int notrace __init						\
 ftrace_define_fields_##call(struct ftrace_event_call *event_call)	\
 {									\
 	struct ftrace_raw_##call field;					\

kernel/trace/trace_export.c

@@ -129,7 +129,7 @@ static void __always_unused ____ftrace_check_##name(void)		\
 
 #undef FTRACE_ENTRY
 #define FTRACE_ENTRY(name, struct_name, id, tstruct, print, filter)	\
-int									\
+static int __init							\
 ftrace_define_fields_##name(struct ftrace_event_call *event_call)	\
 {									\
 	struct struct_name field;					\