bpf: libbpf: don't specify prog name if kernel doesn't support it

Use recently added capability check.

See commit 23499442 ("bpf: libbpf: retry map creation without
the name") for rationale.

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