X86: Simplify X86WindowsTargetObjectFile::getSectionForConstant

There exists a helper function to abstract away the various differences
between ConstantVector, ConstantDataVector, ConstantAggregateZero, etc.

Use it to simplify X86WindowsTargetObjectFile::getSectionForConstant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213104 91177308-0d34-0410-b5e6-96231b3b80d8