tcp: add tracing of skb/skaddr in tcp_event_sk_skb class

Printing the addresses can help us identify the exact skb/sk
for those system in which it's not that easy to run BPF program.
As we can see, it already fetches those, then use it directly
and it will print like below:

...tcp_retransmit_skb: skbaddr=XXX skaddr=XXX family=AF_INET...
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/trace/events/tcp.h

@@ -88,7 +88,8 @@ DECLARE_EVENT_CLASS(tcp_event_sk_skb,
 			      sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
 	),
 
-	TP_printk("family=%s sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c state=%s",
+	TP_printk("skbaddr=%p skaddr=%p family=%s sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c state=%s",
+		  __entry->skbaddr, __entry->skaddr,
 		  show_family_name(__entry->family),
 		  __entry->sport, __entry->dport, __entry->saddr, __entry->daddr,
 		  __entry->saddr_v6, __entry->daddr_v6,