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/lib/Target/AMDGPU/AMDGPUSubtarget.h b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
index c8414f9..bc43a68 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
@@ -85,6 +85,7 @@
   bool FP64FP16Denormals;
   bool FPExceptions;
   bool FlatForGlobal;
+  bool NoAddr64;
   bool UnalignedScratchAccess;
   bool UnalignedBufferAccess;
   bool EnableXNACK;