AMDGPU: Cleanup fmin/fmax legacy function

Use a more specific subtarget check and combine hasOneUse checks

llvm-svn: 293726
diff --git a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
index c31af80..8125550 100644
--- a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
@@ -916,7 +916,7 @@
 
   if (VT == MVT::f32) {
     DAGCombinerInfo DCI(DAG, AfterLegalizeVectorOps, true, nullptr);
-    SDValue MinMax = CombineFMinMaxLegacy(DL, VT, LHS, RHS, True, False, CC, DCI);
+    SDValue MinMax = combineFMinMaxLegacy(DL, VT, LHS, RHS, True, False, CC, DCI);
     if (MinMax)
       return MinMax;
   }