DebugInfo: Factor out common functionality for rendering debug_loc and debug_loc.dwo location list entries

In preparation for refactoring this function into two, one for
debug_loc, one for debug_loc.dwo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205324 91177308-0d34-0410-b5e6-96231b3b80d8