[Atomics] Remove Atomics code stubs; use TF ops

src/compiler/mips/code-generator-mips.cc

Index: src/compiler/mips/code-generator-mips.cc
diff --git a/src/compiler/mips/code-generator-mips.cc b/src/compiler/mips/code-generator-mips.cc
index 453d553d8c8e28e822a1af9d2edd0dc9f69eb04d..c592cecd6f22ae82458feee86eafeced3d392777 100644
--- a/src/compiler/mips/code-generator-mips.cc
+++ b/src/compiler/mips/code-generator-mips.cc
@@ -1324,6 +1324,13 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kCheckedStoreWord64:
       UNREACHABLE();  // currently unsupported checked int64 load/store.
       break;
+    case kAtomicLoadInt8:
+    case kAtomicLoadUint8:
+    case kAtomicLoadInt16:
+    case kAtomicLoadUint16:
+    case kAtomicLoadWord32:
+      UNIMPLEMENTED();
+      break;
   }
 }  // NOLINT(readability/fn_size)