[intrinsics] Drop the now obsolete %_DoubleHi and %_DoubleLo intrinsics.

src/crankshaft/mips64/lithium-mips64.cc

Index: src/crankshaft/mips64/lithium-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-mips64.cc b/src/crankshaft/mips64/lithium-mips64.cc
index b682d19e6f8622d6776fe4f17e53dc4536ee7135..6210bbe1db24ccab5b18f4cc73441f1edbd0bab7 100644
--- a/src/crankshaft/mips64/lithium-mips64.cc
+++ b/src/crankshaft/mips64/lithium-mips64.cc
@@ -1930,13 +1930,6 @@ LInstruction* LChunkBuilder::DoClampToUint8(HClampToUint8* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoDoubleBits(HDoubleBits* instr) {
-  HValue* value = instr->value();
-  DCHECK(value->representation().IsDouble());
-  return DefineAsRegister(new(zone()) LDoubleBits(UseRegister(value)));
-}
-
-
 LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
   LOperand* context = info()->IsStub()
       ? UseFixed(instr->context(), cp)