bpf: tcp: Fix type confusion in bpf_skc_to_tcp6_sock().

bpf: tcp: Fix type confusion in bpf_skc_to_tcp6_sock().

bpf_skc_to_tcp6_sock() only checks if sk->sk_protocol is IPPROTO_TCP
and sk->sk_family is AF_INET6, but RAW socket can bypass it:

  socket(AF_INET6, SOCK_RAW, IPPROTO_TCP)

Let's check sk->sk_type too.

Fixes: af7ec1383361 ("bpf: Add bpf_skc_to_tcp6_sock() helper")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260504210610.180150-6-kuniyu@google.com