As of now, there're two sk_family are traced with sock:inet_sock_set_state,
which are AF_INET and AF_INET6.
So the sk_family are exposed as well.
Then we can conveniently use it to do the filter.

Both sk_family and sk_protocol are showed in the printk message, so we need
not expose them as tracepoint arguments.
Suggested-by: Brendan Gregg <brendan.d.gregg@gmail.com>
Suggested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>