perf kmem: introduce --list-cmds for use by scripts

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
perf mem: introduce --list-cmds for use by scripts

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
perf lock: introduce --list-cmds for use by scripts

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
perf sched: introduce --list-cmds for use by scripts

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>