[AMDGPU] Fix lowering OpenCL enqueue_kernel

One addrspacecast disappeared in clang emitted IR for
block invoke function due to adoption of the new
addr space mapping.

Differential Revision: https://reviews.llvm.org/D43785


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326806 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed