ARM: Make use of d16-d31 when available.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 39e239a1cbf9ad82910ef1ee7ca659ea694ea027..2b24f1212f6ac403997bb2fab518c4d4f2d9ce94 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3690,7 +3690,7 @@ void LCodeGen::DoMathPowHalf(LUnaryMathOperation* instr) {
   __ b(&done, eq);
 
   // Add +0 to convert -0 to +0.
-  __ vadd(result, input, kDoubleRegZero);
+  __ vadd(result, input, DwVfpRegister::ZeroReg());
   __ vsqrt(result, result);
   __ bind(&done);
 }