AMDGPU: Use gfx9 instead of gfx8 in a test

They are the same for the purposes of the tests,
but it's much easier to write check lines for
the memory instructions with offsets.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348643 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed