Revert of [x86] Use AVX in Crankshaft when available.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index b3f6d03acdacc641c48eed2dacdcc61fadc09330..c1831af84bf366c9df5a8a38d68925fad6523bf3 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -748,8 +748,7 @@
     LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
     LOperand* right = UseRegisterAtStart(instr->BetterRightOperand());
     LArithmeticD* result = new(zone()) LArithmeticD(op, left, right);
-    return CpuFeatures::IsSupported(AVX) ? DefineAsRegister(result)
-                                         : DefineSameAsFirst(result);
+    return DefineSameAsFirst(result);
   }
 }