MIPS: Fix bad RegisterConfiguration usage in InstructionSequence unit tests.

src/compiler/instruction.cc

Index: src/compiler/instruction.cc
diff --git a/src/compiler/instruction.cc b/src/compiler/instruction.cc
index 174ee300fee63348fbf0791801528d628da2b2a2..44d525e2c5d4de6a99de33b022be2f6c307f5ba2 100644
--- a/src/compiler/instruction.cc
+++ b/src/compiler/instruction.cc
@@ -12,7 +12,8 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
-const auto GetRegConfig = RegisterConfiguration::Turbofan;
+const RegisterConfiguration* (*GetRegConfig)() =
+    RegisterConfiguration::Turbofan;
 
 FlagsCondition CommuteFlagsCondition(FlagsCondition condition) {
   switch (condition) {
@@ -981,6 +982,11 @@ void InstructionSequence::PrintBlock(int block_id) const {
   PrintBlock(GetRegConfig(), block_id);
 }
 
+const RegisterConfiguration*
+InstructionSequence::GetRegisterConfigurationForTesting() {
+  return GetRegConfig();
+}
+
 FrameStateDescriptor::FrameStateDescriptor(
     Zone* zone, FrameStateType type, BailoutId bailout_id,
     OutputFrameStateCombine state_combine, size_t parameters_count,