Fix DENYLIST format

[chantra]

We started to use 3-column format in https://github.com/kernel-patches/bpf/blob/bpf-next/tools/testing/selftests/bpf/DENYLIST.s390x, where the 3rd column identify where the problem is stemming from.

It would be useful to have the format

1. captured as a header of the file
2. used in the existing files so the next person that updates the file know what to put in.

[anakryiko]

it's not 3-column format, it's a list of test specifiers and everything after # is a comment. Do you mean to enforce some particular format of a comment or what is this about?

[chantra]

it's not 3-column format, it's a list of test specifiers and everything after # is a comment.
Yeah, I think it is a loose-3-column-format. @danielocfb commented about this in the PR. Is that what you meant (test# commentfailing_category)?

[danielocfb]

it's not 3-column format, it's a list of test specifiers and everything after # is a comment.
Yeah, I think it is a loose-3-column-format. @danielocfb commented about this in the PR. Is that what you meant (test# commentfailing_category)?

Yes, what we do in other deny lists. https://github.com/kernel-patches/bpf/blob/bpf-next/tools/testing/selftests/bpf/README.rst#denylisting-tests