s390: fix emit_code_target in assembler

R=bjaideep@ca.ibm.com, joransiu@ca.ibm.com

Bug: 
Change-Id: I83d3c7c2a318eb6c1c4025603b01e894f196bac6
Reviewed-on: https://chromium-review.googlesource.com/655131
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Reviewed-by: Jaideep Bajwa <bjaideep@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#47903}

src/s390/assembler-s390-inl.h

@@ -269,7 +269,7 @@ int32_t Assembler::emit_code_target(Handle<Code> target,
 
   size_t current = code_targets_.size();
   if (current > 0 && !target.is_null() &&
-      code_targets_.back().is_identical_to(target)) {
+      code_targets_.back().address() == target.address()) {
     // Optimization if we keep jumping to the same code target.
     current--;
   } else {