[turbofan] Remove the FloatXXSubPreserveNan operators.

src/mips/macro-assembler-mips.h

Index: src/mips/macro-assembler-mips.h
diff --git a/src/mips/macro-assembler-mips.h b/src/mips/macro-assembler-mips.h
index 1e60bea2e9215c39eda582cc6ba74cbef0d229a3..18698c162df51f22b66f5bbdb11392dbee48c724 100644
--- a/src/mips/macro-assembler-mips.h
+++ b/src/mips/macro-assembler-mips.h
@@ -875,12 +875,6 @@ class MacroAssembler: public Assembler {
   void Floor_w_d(FPURegister fd, FPURegister fs);
   void Ceil_w_d(FPURegister fd, FPURegister fs);
 
-  // Preserve value of a NaN operand
-  void SubNanPreservePayloadAndSign_s(FPURegister fd, FPURegister fs,
-                                      FPURegister ft);
-  void SubNanPreservePayloadAndSign_d(FPURegister fd, FPURegister fs,
-                                      FPURegister ft);
-
   // FP32 mode: Move the general purpose register into
   // the high part of the double-register pair.
   // FP64 mode: Move the general-purpose register into