Revert r360902 "Resubmit: [Salvage] Change salvage debug info ..."

This reverts commit rr360902. It caused an assertion failure in
lib/IR/DebugInfoMetadata.cpp: Assertion `(OffsetInBits + SizeInBits <=
FragmentSizeInBits) && "new fragment outside of original fragment"'
failed.

PR41931.

llvm-svn: 361246