ftrace: Clean comments related to FTRACE_OPS_FL_PER_CPU

Commit b3a88803 ("ftrace: Kill FTRACE_OPS_FL_PER_CPU") didn't
completely remove the comments related to FTRACE_OPS_FL_PER_CPU.

Link: https://lkml.kernel.org/r/20221025153923.1995973-1-zhengyejian1@huawei.com



Fixes: b3a88803 ("ftrace: Kill FTRACE_OPS_FL_PER_CPU")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>