[Utils] Salvage debug info from dead 'or' instructions

Extend salvageDebugInfo to preserve the debug info from a dead 'or'
with a constant.

Patch by Ismail Badawi!

Differential Revision: https://reviews.llvm.org/D43129

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324764 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed