this PR is intended as first attempt for upgrade bootloader in SLE-12 and I do a bit cleaning here for this reason. I want to focus always when cleaning on the most critical issue and for bootloader it is bunch of obsolete code. That is why I do not convert it to logging. If we want in future remove these builtins, then we probably spend a lot of time when modifiing it. So it you do big changes in file, I agree that new logging way is better, but when code is critical and I do mostly smaller changes to not break it much, then additional changes is much welcome, especially if code is not covered in tests, so every typo will end in crash in released code.