Interpreter: fix build.

Due to unfortunate commit timing.

Test: make build-art-host
Change-Id: Ie523399309b20836ab9f7a8a8224c5cb41bc79fc
diff --git a/runtime/interpreter/interpreter_common.cc b/runtime/interpreter/interpreter_common.cc
index 41673f4..179e48b 100644
--- a/runtime/interpreter/interpreter_common.cc
+++ b/runtime/interpreter/interpreter_common.cc
@@ -936,12 +936,12 @@
 
     switch (handle_kind) {
       case kInstanceGet: {
-        ObjPtr<mirror::Object> obj = shadow_frame.GetVRegReference(receiver_vregC);
+        ObjPtr<mirror::Object> obj = shadow_frame.GetVRegReference(first_src_reg);
         DoFieldGetForInvokePolymorphic(self, shadow_frame, obj, field, field_type, result);
         return true;
       }
       case kInstancePut: {
-        ObjPtr<mirror::Object> obj = shadow_frame.GetVRegReference(receiver_vregC);
+        ObjPtr<mirror::Object> obj = shadow_frame.GetVRegReference(first_src_reg);
         return DoFieldPutForInvokePolymorphic(self, shadow_frame, obj, field, field_type, arg[1]);
       }
       case kStaticGet: {