DwarfDebug: Remove trivial function wrapper

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196445 91177308-0d34-0410-b5e6-96231b3b80d8
DwarfDebug: Avoid unnecessary abbreviation lookup when emitting DIEs

DIEs already contain references directly to their DIEAbbrev, use that
instead of looking it up based on index.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196446 91177308-0d34-0410-b5e6-96231b3b80d8