Fix has_constant_parameter_count() confusion in LReturn

src/arm64/lithium-codegen-arm64.cc

Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index 1b8ae1b9c145f90fe36fc319cf980d54cf073f93..9fe311c939277109a7348a5b7ff48cc4770f31c1 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -4766,6 +4766,7 @@ void LCodeGen::DoReturn(LReturn* instr) {
     int parameter_count = ToInteger32(instr->constant_parameter_count());
     __ Drop(parameter_count + 1);
   } else {
+    DCHECK(info()->IsStub());  // Functions would need to drop one more value.
     Register parameter_count = ToRegister(instr->parameter_count());
     __ DropBySMI(parameter_count);
   }