NVPTX: Replace uses of cuda.syncthreads with nvvm.barrier0

Everywhere where cuda.syncthreads or __syncthreads is used, use the
properly namespaced nvvm.barrier0 instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274664 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed