[turbofan] Hook up the shift code stubs with TurboFan.

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index 18ac9f9f3215b848d3a532098e8f577b909d0860..4a34575f11fc0ea4287b56270293f712cc366fec 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -2278,9 +2278,6 @@ void CodeGenerator::AssembleJumpTable(Label** targets, size_t target_count) {
 }
 
 
-void CodeGenerator::AddNopForSmiCodeInlining() { __ nop(); }
-
-
 void CodeGenerator::EnsureSpaceForLazyDeopt() {
   if (!info()->ShouldEnsureSpaceForLazyDeopt()) {
     return;