Revert D76519 "[NFC] Refactor how CFI section types are represented in AsmPrinter"

This reverts commit 0ce723cb.

D76519 was not quite NFC. If we see a CFISection::Debug function before a
CFISection::EH one (-fexceptions -fno-asynchronous-unwind-tables), we may
incorrectly pick CFISection::Debug and emit a `.cfi_sections .debug_frame`.
We should use .eh_frame instead.

This scenario is untested.