PPC: Pad InterpreterEntryTrampoline end with bkpt instruction.

While execution will not return to this location, stack iteration
logic will attempt to find the code object associated with the return
address.  This makes sure that it maps to the correct object and not
to the one immediately following it in memory.

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1490343002

Cr-Commit-Position: refs/heads/master@{#32526}

src/ppc/builtins-ppc.cc

@@ -858,6 +858,7 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   // and header removal.
   __ addi(ip, ip, Operand(Code::kHeaderSize - kHeapObjectTag));
   __ Call(ip);
+  __ bkpt(0);  // Does not return here.
 }