Add dummy implementation for turbofan unsupported platform.

   This function is defined in feb28907.
   (https://codereview.chromium.org/892513003).

   original commit message:
    [turbofan] Initial support for Switch.

    Adds Switch and Case operators to TurboFan and handles them
    appropriately in instruction selection and code generation.

BUG=

Review URL: https://codereview.chromium.org/902943005

Cr-Commit-Position: refs/heads/master@{#26533}

src/compiler/code-generator.cc

@@ -611,6 +611,11 @@ void CodeGenerator::AssembleSwap(InstructionOperand* source,
 
 void CodeGenerator::AddNopForSmiCodeInlining() { UNIMPLEMENTED(); }
 
+
+void CodeGenerator::AssembleJumpTable(Label** targets, size_t target_count) {
+  UNIMPLEMENTED();
+}
+
 #endif  // !V8_TURBOFAN_BACKEND