Temporary disable new round implementation on x86/x86_64

Rationale:
FUGU is not happy

Test: 580-checker-round

BUG=26327751

Change-Id: If0ddea47a88e14b86d37080b8a18a6f8defcc8e6
diff --git a/compiler/optimizing/intrinsics_x86.cc b/compiler/optimizing/intrinsics_x86.cc
index 83cc278..725c55c 100644
--- a/compiler/optimizing/intrinsics_x86.cc
+++ b/compiler/optimizing/intrinsics_x86.cc
@@ -753,6 +753,11 @@
 }
 
 void IntrinsicLocationsBuilderX86::VisitMathRoundFloat(HInvoke* invoke) {
+  // See intrinsics.h.
+  if (!kRoundIsPlusPointFive) {
+    return;
+  }
+
   // Do we have instruction support?
   if (codegen_->GetInstructionSetFeatures().HasSSE4_1()) {
     HInvokeStaticOrDirect* static_or_direct = invoke->AsInvokeStaticOrDirect();