ftrace: don't try to __ftrace_replace_code on !FTRACE_FL_CONVERTED rec

Do __ftrace_replace_code for !FTRACE_FL_CONVERTED rec will always
fail, we should ignore this rec.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: "Steven Rostedt ;" <rostedt@goodmis.org>
LKML-Reference: <49BA2472.4060206@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>