[COFF] Expose an easier helper function for getting names for relocation types

The existing method is protected, and requires using DataRefImpl
and SmallVector.

Differential Revision: https://reviews.llvm.org/D50995

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340725 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed