[crankshaft] Remove the useless HMapEnumLength instruction.

src/crankshaft/mips/lithium-codegen-mips.cc

Index: src/crankshaft/mips/lithium-codegen-mips.cc
diff --git a/src/crankshaft/mips/lithium-codegen-mips.cc b/src/crankshaft/mips/lithium-codegen-mips.cc
index 4e3352076fe8eb60c162a5c7896effd4b66e935c..4c8b439120533a2beefbcf00f5be752785d06cbc 100644
--- a/src/crankshaft/mips/lithium-codegen-mips.cc
+++ b/src/crankshaft/mips/lithium-codegen-mips.cc
@@ -1651,13 +1651,6 @@ void LCodeGen::DoConstantT(LConstantT* instr) {
 }
 
 
-void LCodeGen::DoMapEnumLength(LMapEnumLength* instr) {
-  Register result = ToRegister(instr->result());
-  Register map = ToRegister(instr->value());
-  __ EnumLength(result, map);
-}
-
-
 MemOperand LCodeGen::BuildSeqStringOperand(Register string,
                                            LOperand* index,
                                            String::Encoding encoding) {