Rename parameters to fix shadow warnings.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@198641 91177308-0d34-0410-b5e6-96231b3b80d8
Remove leading underscore from parameters.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@198642 91177308-0d34-0410-b5e6-96231b3b80d8