Eliminate redundant descriptor ElementTransitionAndStoreDescriptor.

src/arm64/interface-descriptors-arm64.cc

Index: src/arm64/interface-descriptors-arm64.cc
diff --git a/src/arm64/interface-descriptors-arm64.cc b/src/arm64/interface-descriptors-arm64.cc
index d175de307cfb1fad118bf386b7c5a68d5515c426..6e13d56c550f67c2528d6932849aaec01db22829 100644
--- a/src/arm64/interface-descriptors-arm64.cc
+++ b/src/arm64/interface-descriptors-arm64.cc
@@ -47,9 +47,6 @@ const Register StoreGlobalViaContextDescriptor::NameRegister() { return x3; }
 const Register StoreGlobalViaContextDescriptor::ValueRegister() { return x0; }
 
 
-const Register ElementTransitionAndStoreDescriptor::MapRegister() { return x3; }
-
-
 const Register InstanceofDescriptor::left() {
   // Object to check (instanceof lhs).
   return x11;