Enable FeatureFlatForGlobal on Volcanic Islands

This switches to the workaround that HSA defaults to
for the mesa path.

This should be applied to the 4.0 branch.

Patch by Vedran Miletić <vedran@miletic.net>

llvm-svn: 292982
diff --git a/llvm/test/CodeGen/AMDGPU/sgpr-copy-duplicate-operand.ll b/llvm/test/CodeGen/AMDGPU/sgpr-copy-duplicate-operand.ll
index df67fcc..f44ae6e 100644
--- a/llvm/test/CodeGen/AMDGPU/sgpr-copy-duplicate-operand.ll
+++ b/llvm/test/CodeGen/AMDGPU/sgpr-copy-duplicate-operand.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=amdgcn -mcpu=SI -verify-machineinstrs< %s | FileCheck -check-prefix=SI %s
+; RUN: llc -march=amdgcn -verify-machineinstrs< %s | FileCheck -check-prefix=SI %s
 ; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs< %s | FileCheck -check-prefix=SI %s
 
 ; Copy VGPR -> SGPR used twice as an instruction operand, which is then