Enforce the restriction that a parameter to a kernel function
cannot be a pointer to the private address space (as clarified
in the OpenCL 1.2 specification).

Patch by Fraser Cormack!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204941 91177308-0d34-0410-b5e6-96231b3b80d8