Revert of [x64] Use vcvtlsi2sd when AVX is enabled

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 461e097cd67c0131531d9945ba0dd06b530b5a8a..ad3827aba572e60eff81d0e83357704bd6bee525 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -788,26 +788,14 @@
 
 
 void MacroAssembler::Cvtlsi2sd(XMMRegister dst, Register src) {
-  if (CpuFeatures::IsSupported(AVX)) {
-    CpuFeatureScope scope(this, AVX);
-    vxorpd(dst, dst, dst);
-    vcvtlsi2sd(dst, dst, src);
-  } else {
-    xorps(dst, dst);
-    cvtlsi2sd(dst, src);
-  }
+  xorps(dst, dst);
+  cvtlsi2sd(dst, src);
 }
 
 
 void MacroAssembler::Cvtlsi2sd(XMMRegister dst, const Operand& src) {
-  if (CpuFeatures::IsSupported(AVX)) {
-    CpuFeatureScope scope(this, AVX);
-    vxorpd(dst, dst, dst);
-    vcvtlsi2sd(dst, dst, src);
-  } else {
-    xorps(dst, dst);
-    cvtlsi2sd(dst, src);
-  }
+  xorps(dst, dst);
+  cvtlsi2sd(dst, src);
 }