The tracing recursion prevention mechanism must be protected by rcu, that
leaves __rcu_read_{lock,unlock} unprotected by this mechanism. If we trace
them, the recursion will happen. Let's add them into the btf id deny list.

When CONFIG_PREEMPT_RCU is enabled, it can be reproduced with a simple bpf
program as such:
  SEC("fentry/__rcu_read_lock")
  int fentry_run()
  {
      return 0;
  }
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230424161104.3737-2-laoar.shao@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>