bpf: BPF_PROG_TYPE_CGROUP_{SKB, SOCK, SOCK_ADDR} require cgroups enabled

There is no way to exercise appropriate attach points without cgroups
enabled. This lets test_verifier correctly skip tests for these
prog_types if kernel was compiled without BPF cgroup support.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>