tracing: Fix compile issue for trace_sched_wakeup.c

The function start_func_tracer() was incorrectly added in the
 #ifdef CONFIG_FUNCTION_TRACER condition, but is still used even
when function tracing is not enabled.

The calls to register_ftrace_function() and register_ftrace_graph()
become nops (and their arguments are even ignored), thus there is
no reason to hide start_func_tracer() when function tracing is
not enabled.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_sched_wakeup.c

@@ -130,6 +130,7 @@ static struct ftrace_ops trace_ops __read_mostly =
 {
 	.func = wakeup_tracer_call,
 };
+#endif /* CONFIG_FUNCTION_TRACER */
 
 static int start_func_tracer(int graph)
 {
@@ -159,8 +160,6 @@ static void stop_func_tracer(int graph)
 		unregister_ftrace_graph();
 }
 
-#endif /* CONFIG_FUNCTION_TRACER */
-
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
 {