selftests/bpf: Avoid pinning prog when attaching to tc ingress in btf_skc_cls_ingress

This patch removes the need to pin prog when attaching to tc ingress
in the btf_skc_cls_ingress test.  Instead, directly use the
bpf_tc_hook_create() and bpf_tc_attach().  The qdisc clsact
will go away together with the netns, so no need to
bpf_tc_hook_destroy().

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20221129070900.3142427-8-martin.lau@linux.dev