Merge pull request #274 from chrisccoulson/efi-remove-deprecated-apis

efi: remove deprecated APIs.

This removes deprecated APIs and test data, and will make it easier to
generate new mock binaries without having to adjust digests in associated
unit tests. I want to generate new mock grub binaries in another PR to add
the EFI prefix.

Note that this removes some data that is used by tools/gen-compattest-data,
but it turns out that a previous PR (#156)
already removed test data required by it and it hasn't worked since then. I need
to rework how we test that changes are backwards compatible, so I'll fix that in
another PR.