ftrace: Nuke clear_ftrace_function

clear_ftrace_function is not used outside of ftrace.c and is not help to
use a function, so nuke it per Steve's suggestion.

Link: http://lkml.kernel.org/r/1517537689-34947-1-git-send-email-xieyisheng1@huawei.com

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/linux/ftrace.h

@@ -223,7 +223,6 @@ extern enum ftrace_tracing_type_t ftrace_tracing_type;
  */
 int register_ftrace_function(struct ftrace_ops *ops);
 int unregister_ftrace_function(struct ftrace_ops *ops);
-void clear_ftrace_function(void);
 
 extern void ftrace_stub(unsigned long a0, unsigned long a1,
 			struct ftrace_ops *op, struct pt_regs *regs);
@@ -239,7 +238,6 @@ static inline int ftrace_nr_registered_ops(void)
 {
 	return 0;
 }
-static inline void clear_ftrace_function(void) { }
 static inline void ftrace_kill(void) { }
 static inline void ftrace_free_init_mem(void) { }
 static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { }

kernel/trace/ftrace.c

@@ -192,17 +192,6 @@ static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
 	op->saved_func(ip, parent_ip, op, regs);
 }
 
-/**
- * clear_ftrace_function - reset the ftrace function
- *
- * This NULLs the ftrace function and in essence stops
- * tracing.  There may be lag
- */
-void clear_ftrace_function(void)
-{
-	ftrace_trace_function = ftrace_stub;
-}
-
 static void ftrace_sync(struct work_struct *work)
 {
 	/*
@@ -6689,7 +6678,7 @@ void ftrace_kill(void)
 {
 	ftrace_disabled = 1;
 	ftrace_enabled = 0;
-	clear_ftrace_function();
+	ftrace_trace_function = ftrace_stub;
 }
 
 /**