Revert "R600: Add new intrinsic to read work dimensions"

This reverts commit r219705.

CodeGen/R600/work-item-intrinsics.ll was failing on linux.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219707 91177308-0d34-0410-b5e6-96231b3b80d8