selftests/bpf: test cases for regsafe() bug skipping check_id()

Under certain conditions it was possible for verifier.c:regsafe() to
skip check_id() call. This commit adds negative test cases previously
errorneously accepted as safe.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20221209135733.28851-3-eddyz87@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>