[interpreter] use GetRegisterCountOperand for OperandType::kRegOutList

Fixes a crash in PrintRegisters() with --trace-ignition and the
RestoreGeneratorRegisters bytecode.

BUG=v8:4280, v8:6351
R=rmcilroy@chromium.org, mythria@chromium.org, adamk@chromium.org

Change-Id: I09e86523b71fb9e5763e0373c567925f38227913
Reviewed-on: https://chromium-review.googlesource.com/523843
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45706}

src/interpreter/bytecode-array-accessor.cc

@@ -142,7 +142,8 @@ int BytecodeArrayAccessor::GetRegisterOperandRange(int operand_index) const {
       Bytecodes::GetOperandTypes(current_bytecode());
   OperandType operand_type = operand_types[operand_index];
   DCHECK(Bytecodes::IsRegisterOperandType(operand_type));
-  if (operand_type == OperandType::kRegList) {
+  if (operand_type == OperandType::kRegList ||
+      operand_type == OperandType::kRegOutList) {
     return GetRegisterCountOperand(operand_index + 1);
   } else {
     return Bytecodes::GetNumberOfRegistersRepresentedBy(operand_type);