[OpenCL] Fix for TBAA information of pointer after addresspacecast

Summary: When addresspacecast is generated resulting pointer should preserve TBAA information from original value.

Reviewers: rjmccall, yaxunl, Anastasia

Reviewed By: rjmccall

Subscribers: asavonic, kosarev, cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D55262

llvm-svn: 348919