AMDGPU: Reorganize store tests

Split by AS.
Merge with some prviously failing tests.

Differential Revision: https://reviews.llvm.org/D23969

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280523 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed