tcp_metrics: use parallel_ops for tcp_metrics_nl_family

TCP_METRICS_CMD_GET and TCP_METRICS_CMD_DEL use their
own locking (tcp_metrics_lock and RCU),
they do not need genl_mutex protection.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240416162025.1251547-1-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>