[DebugInfo] Fix printing CIE offsets in EH FDEs.

While the value of the CIE pointer field in a DWARF FDE record is
an offset to the corresponding CIE record from the beginning of
the section, for EH FDE records it is relative to the current offset.
Previously, we did not make that distinction when dumped both kinds
of FDE records and just printed the same value for the CIE pointer
field and the CIE offset; that was acceptable for DWARF FDEs but was
wrong for EH FDEs.

This patch fixes the issue by explicitly printing the offset of the
linked CIE object.

Differential Revision: https://reviews.llvm.org/D74613