[turbofan] Increase the number of inputs for Binop instructions further

In WebAssembly benchmarks I saw Binop instructions with 6 inputs. We
don't know how many inputs there can actually be, so we conservatively
increase the number to 8 now.

R=jarin@chromium.org
Bug=chromium:842501

Change-Id: Id087481e7e524006c2f03fc545f9e35d1cad1fe8
Reviewed-on: https://chromium-review.googlesource.com/1061114Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53207}

src/compiler/x64/instruction-selector-x64.cc

@@ -427,7 +427,7 @@ static void VisitBinop(InstructionSelector* selector, Node* node,
   Int32BinopMatcher m(node);
   Node* left = m.left().node();
   Node* right = m.right().node();
-  InstructionOperand inputs[5];
+  InstructionOperand inputs[8];
   size_t input_count = 0;
   InstructionOperand outputs[1];
   size_t output_count = 0;