AMDGPU: Do not test for SI in getIsaVersion

SI is being tested by isa version in the first two if statements of the function.

llvm-svn: 307573
diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
index 26515b2..ca7ae3f 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
@@ -142,7 +142,7 @@
   if (Features.test(FeatureISAVersion9_0_3))
     return {9, 0, 3};
 
-  if (!Features.test(FeatureGCN) || Features.test(FeatureSouthernIslands))
+  if (!Features.test(FeatureGCN))
     return {0, 0, 0};
   return {7, 0, 0};
 }