trace: tcp: Add const qualifier to skb parameter in tcp_probe event

Change the tcp_probe tracepoint to accept a const struct sk_buff
parameter instead of a non-const one. This improves type safety and
better reflects that the skb is not modified within the tracepoint
implementation.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250416-tcp_probe-v1-1-1edc3c5a1cb8@debian.org


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