tracing: Remove ftrace() function

The only caller of function ftrace(...) was removed a long time ago,
so remove the function body as well.

Link: http://lkml.kernel.org/r/1365564393-10972-10-git-send-email-jovi.zhangwei@huawei.com



Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>