Create a typedef for HInstruction::GetInputs() return type.

And some other cleanup after
    https://android-review.googlesource.com/230742

Test: No new tests. ART test suite passed (tested on host).
Change-Id: I4743bf17544d0234c6ccb46dd0c1b9aae5c93e17
diff --git a/compiler/optimizing/code_generator.cc b/compiler/optimizing/code_generator.cc
index 12aa152..4520f9b 100644
--- a/compiler/optimizing/code_generator.cc
+++ b/compiler/optimizing/code_generator.cc
@@ -111,7 +111,7 @@
         << " " << locations->Out();
   }
 
-  auto&& inputs = instruction->GetInputs();
+  HConstInputsRef inputs = instruction->GetInputs();
   for (size_t i = 0; i < inputs.size(); ++i) {
     DCHECK(CheckType(inputs[i]->GetType(), locations->InAt(i)))
       << inputs[i]->GetType() << " " << locations->InAt(i);