kprobes: freelist.h removed

This patch will remove freelist.h from kernel source tree, since the
only use cases (kretprobe and rethook) are converted to objpool.

Link: https://lore.kernel.org/all/20231017135654.82270-5-wuqiang.matt@bytedance.com/

Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>