libbpf: Fix LIBBPF_1.0.0 declaration in libbpf.map

Add the missing LIBBPF_0.8.0 at the end of the LIBBPF_1.0.0 declaration,
similarly to other version declarations.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221006110736.84253-2-roberto.sassu@huaweicloud.com