R600/SI: Add lit tests for llvm.SI.imageload and llvm.SI.resinfo intrinsics

Adapted from the llvm.SI.sample test.

Reviewed-by: Christian König <christian.koenig@amd.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181425 91177308-0d34-0410-b5e6-96231b3b80d8