tracing/function-return-tracer: clean up task start/exit callbacks

Impact: cleanup

Eliminate #ifdefs in core code by using empty inline functions.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 2ba259b..938ca19 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -335,6 +335,9 @@
 
 extern void ftrace_retfunc_init_task(struct task_struct *t);
 extern void ftrace_retfunc_exit_task(struct task_struct *t);
+#else
+static inline void ftrace_retfunc_init_task(struct task_struct *t) { }
+static inline void ftrace_retfunc_exit_task(struct task_struct *t) { }
 #endif
 
 #endif /* _LINUX_FTRACE_H */