X87: [turbofan] Make Float32Neg and Float64Neg mandatory operators.

  port 6c44ab30 (r38399)

  original commit message:

BUG=

Review-Url: https://codereview.chromium.org/2221323002
Cr-Commit-Position: refs/heads/master@{#38476}

src/compiler/x87/instruction-selector-x87.cc

@@ -1723,8 +1723,7 @@ void InstructionSelector::VisitAtomicStore(Node* node) {
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
   MachineOperatorBuilder::Flags flags =
-      MachineOperatorBuilder::kWord32ShiftIsSafe |
-      MachineOperatorBuilder::kFloat32Neg | MachineOperatorBuilder::kFloat64Neg;
+      MachineOperatorBuilder::kWord32ShiftIsSafe;
   if (CpuFeatures::IsSupported(POPCNT)) {
     flags |= MachineOperatorBuilder::kWord32Popcnt;
   }