bpf-firewall: properly handle kernels where BPF cgroup is disabled but TRIE...

bpf-firewall: properly handle kernels where BPF cgroup is disabled but TRIE maps are enabled (#7298)

So far, we assumed that kernels where TRIE was on also supported
BPF/cgroup stuff. That's not a correct assumption to make, hence check
for both features separately.

Fixes: #7054