MIPS: Fix [stubs] Introduce a dedicated FastNewObjectStub

Typo in implementation of FastNewObjectStub::Generate for MIPS32
cause unnecessary calls to slow Runtime::kNewObject

TEST=cctest/test-heap-profiler/TrackBumpPointerAllocations
BUG=

Review URL: https://codereview.chromium.org/1762263002

Cr-Commit-Position: refs/heads/master@{#34490}

src/mips/code-stubs-mips.cc

@@ -4749,7 +4749,7 @@ void FastNewObjectStub::Generate(MacroAssembler* masm) {
   __ lw(a2, FieldMemOperand(a3, JSFunction::kPrototypeOrInitialMapOffset));
   __ JumpIfSmi(a2, &new_object);
   __ GetObjectType(a2, a0, a0);
-  __ Branch(&new_object, ne, a2, Operand(MAP_TYPE));
+  __ Branch(&new_object, ne, a0, Operand(MAP_TYPE));
 
   // Fall back to runtime if the target differs from the new target's
   // initial map constructor.