MIPS: Remove madd.d usage for r6.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index c7f3517a8e13e157cf6c75c85aafa83df42ebddf..7d5ffadd49aaa12e621d75569cdfef82bc575a9f 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1517,7 +1517,7 @@ LInstruction* LChunkBuilder::DoMul(HMul* instr) {
     return DefineAsRegister(mul);
 
   } else if (instr->representation().IsDouble()) {
-    if (IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6)) {
+    if (IsMipsArchVariant(kMips32r2)) {
       if (instr->HasOneUse() && instr->uses().value()->IsAdd()) {
         HAdd* add = HAdd::cast(instr->uses().value());
         if (instr == add->left()) {
@@ -1590,7 +1590,7 @@ LInstruction* LChunkBuilder::DoAdd(HAdd* instr) {
     LInstruction* result = DefineAsRegister(add);
     return result;
   } else if (instr->representation().IsDouble()) {
-    if (IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6)) {
+    if (IsMipsArchVariant(kMips32r2)) {
       if (instr->left()->IsMul())
         return DoMultiplyAdd(HMul::cast(instr->left()), instr->right());