MIPS64: Improve UInt32 to Double conversion.

src/compiler/mips64/code-generator-mips64.cc

Index: src/compiler/mips64/code-generator-mips64.cc
diff --git a/src/compiler/mips64/code-generator-mips64.cc b/src/compiler/mips64/code-generator-mips64.cc
index e0e291311c35f3efba7207c5168ee728fd1c5640..beea307995d69982c4abc67986614daf2eb7b353 100644
--- a/src/compiler/mips64/code-generator-mips64.cc
+++ b/src/compiler/mips64/code-generator-mips64.cc
@@ -953,8 +953,7 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       break;
     }
     case kMips64CvtDUw: {
-      FPURegister scratch = kScratchDoubleReg;
-      __ Cvt_d_uw(i.OutputDoubleRegister(), i.InputRegister(0), scratch);
+      __ Cvt_d_uw(i.OutputDoubleRegister(), i.InputRegister(0));
       break;
     }
     case kMips64CvtDUl: {