net: Implement missing SO_TIMESTAMPING_NEW cmsg support

Commit 9718475e ("socket: Add SO_TIMESTAMPING_NEW") added the new
socket option SO_TIMESTAMPING_NEW. However, it was never implemented in
__sock_cmsg_send thus breaking SO_TIMESTAMPING cmsg for platforms using
SO_TIMESTAMPING_NEW.

Fixes: 9718475e ("socket: Add SO_TIMESTAMPING_NEW")
Link: https://lore.kernel.org/netdev/6a7281bf-bc4a-4f75-bb88-7011908ae471@app.fastmail.com/Signed-off-by: Thomas Lange <thomas@corelatus.se>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240104085744.49164-1-thomas@corelatus.seSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/sock.c

@@ -2813,6 +2813,7 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
 		sockc->mark = *(u32 *)CMSG_DATA(cmsg);
 		break;
 	case SO_TIMESTAMPING_OLD:
+	case SO_TIMESTAMPING_NEW:
 		if (cmsg->cmsg_len != CMSG_LEN(sizeof(u32)))
 			return -EINVAL;