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/load-local-i8.ll b/llvm/test/CodeGen/AMDGPU/load-local-i8.ll
index 6fd6f4d..9ffc742 100644
--- a/llvm/test/CodeGen/AMDGPU/load-local-i8.ll
+++ b/llvm/test/CodeGen/AMDGPU/load-local-i8.ll
@@ -142,7 +142,7 @@
 ; GCN: s_mov_b32 m0
 ; GCN: ds_read_u16
 ; FIXME: Need to optimize this sequence to avoid extra shift on VI.
-;         t23: i16 = srl t39, Constant:i32<8> 
+;         t23: i16 = srl t39, Constant:i32<8>
 ;          t31: i32 = any_extend t23
 ;        t33: i32 = sign_extend_inreg t31, ValueType:ch:i8