[OpenCL] Remove access qualifiers on images in arg info metadata.

Summary:
Remove access qualifiers on images in arg info metadata:
 * kernel_arg_type
 * kernel_arg_base_type

Image access qualifiers are inseparable from type in clang implementation,
but OpenCL spec provides a special query to get access qualifier
via clGetKernelArgInfo with CL_KERNEL_ARG_ACCESS_QUALIFIER.

Besides that OpenCL conformance test_api get_kernel_arg_info expects
image types without access qualifier.

Patch by Evgeniy Tyurin.

Reviewers: bader, yaxunl, Anastasia

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D23915

llvm-svn: 280699