[deoptimizer,ppc] Fix bug: constant pool reg had wrong value

This fixes a typo where we stored the framepointer in the constant pool
register instead of the constant pool value.

Bug: v8:7915
Change-Id: I612bf1860ed2e5e5707e2df4a2b92aefaaa9c5cb
Reviewed-on: https://chromium-review.googlesource.com/1127639Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54283}

src/deoptimizer.cc

@@ -1315,7 +1315,7 @@ void Deoptimizer::DoComputeConstructStubFrame(TranslatedFrame* translated_frame,
     if (is_topmost) {
       Register constant_pool_reg =
           JavaScriptFrame::constant_pool_pointer_register();
-      output_frame->SetRegister(constant_pool_reg.code(), fp_value);
+      output_frame->SetRegister(constant_pool_reg.code(), constant_pool_value);
     }
   }