MIPS: Fix 'MIPS: Move Maps' back pointers from "transitions" to "constructor" field'.

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index de3c08afff060855886bbdf8490e51fb1fad6b59..6c07e6863af97f882c20c16f97a2b356775a9ca5 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -4387,7 +4387,7 @@ void MacroAssembler::TryGetFunctionPrototype(Register function,
     // Non-instance prototype: Fetch prototype from constructor field
     // in initial map.
     bind(&non_instance);
-    GetMapConstructor(result, result, scratch, at);
+    GetMapConstructor(result, result, scratch, scratch);
   }
 
   // All done.