sk is already allocated in inet_create/inet6_create, hence when
BPF_CGROUP_RUN_PROG_INET_SOCK is executed sk will never be NULL.

The logic is as bellow,
	sk = sk_alloc();
	if (!sk)
		goto out;
	BPF_CGROUP_RUN_PROG_INET_SOCK(sk);
Signed-off-by: NYafang Shao <laoar.shao@gmail.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>