MIPS: Refactor code for unresolved field entrypoint.

This is a follow-up to
https://android-review.googlesource.com/#/c/325423/.

Test: booted MIPS32R2 in QEMU
Test: test-art-target-run-test-optimizing in QEMU
Test: booted MIPS64 (with 2nd arch MIPS32R6) in QEMU
Test: test-art-target-run-test-optimizing
      (MIPS64R6 and MIPS32R6) in QEMU

Change-Id: Ie663ecf0489e7b182434708bef71686df5f37273
diff --git a/compiler/optimizing/code_generator_mips64.h b/compiler/optimizing/code_generator_mips64.h
index 52b780c..5ba8912 100644
--- a/compiler/optimizing/code_generator_mips64.h
+++ b/compiler/optimizing/code_generator_mips64.h
@@ -115,12 +115,11 @@
   Location GetReturnLocation(Primitive::Type type ATTRIBUTE_UNUSED) const OVERRIDE {
     return Location::RegisterLocation(V0);
   }
-  Location GetSetValueLocation(Primitive::Type type, bool is_instance) const OVERRIDE {
-    return Primitive::Is64BitType(type)
+  Location GetSetValueLocation(Primitive::Type type ATTRIBUTE_UNUSED,
+                               bool is_instance) const OVERRIDE {
+    return is_instance
         ? Location::RegisterLocation(A2)
-        : (is_instance
-            ? Location::RegisterLocation(A2)
-            : Location::RegisterLocation(A1));
+        : Location::RegisterLocation(A1);
   }
   Location GetFpuLocation(Primitive::Type type ATTRIBUTE_UNUSED) const OVERRIDE {
     return Location::FpuRegisterLocation(F0);