[PECOFF][Writer] Remove duplicated code by moving it to parent class.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@185200 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF][Writer] Fix wrong section header.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@185205 91177308-0d34-0410-b5e6-96231b3b80d8