selftests/bpf: Ensure the unsupported struct_ops prog cannot be loaded

selftests/bpf: Ensure the unsupported struct_ops prog cannot be loaded

There is an existing "bpf_tcp_ca/unsupp_cong_op" test to ensure
the unsupported tcp-cc "get_info" struct_ops prog cannot be loaded.

This patch adds a new test in the bpf_testmod such that the
unsupported ops test does not depend on other kernel subsystem
where its supporting ops may be changed in the future.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240722183049.2254692-4-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>