[PECOFF] Move a utility function used in a pass to Pass.cpp.

The file currently has only one function. Function that is useful both for
IdataPass and EdataPass will be added to that file.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@197140 91177308-0d34-0410-b5e6-96231b3b80d8