Revert of Add unoptimized/optimized variants of MathFloor TF code stub

src/x64/interface-descriptors-x64.cc

Index: src/x64/interface-descriptors-x64.cc
diff --git a/src/x64/interface-descriptors-x64.cc b/src/x64/interface-descriptors-x64.cc
index 4f43569c35caca2ddbbbeaaaba70e7bc2e226325..7602403508739cdcce27f420bda349b3ec32f742 100644
--- a/src/x64/interface-descriptors-x64.cc
+++ b/src/x64/interface-descriptors-x64.cc
@@ -332,25 +332,14 @@
 }
 
 
-void MathRoundVariantCallFromUnoptimizedCodeDescriptor::
-    InitializePlatformSpecific(CallInterfaceDescriptorData* data) {
+void MathRoundVariantDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
   Register registers[] = {
       rdi,  // math rounding function
       rdx,  // vector slot id
   };
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
-
-
-void MathRoundVariantCallFromOptimizedCodeDescriptor::
-    InitializePlatformSpecific(CallInterfaceDescriptorData* data) {
-  Register registers[] = {
-      rdi,  // math rounding function
-      rdx,  // vector slot id
-      rbx   // type vector
-  };
-  data->InitializePlatformSpecific(arraysize(registers), registers);
-}
 }  // namespace internal
 }  // namespace v8