ART: Move JNI files to runtime/jni/ .

Test: Rely on TreeHugger.
Change-Id: I9cae11191ef1567ae9453be498882a7767285140
diff --git a/runtime/native/java_lang_ref_Reference.cc b/runtime/native/java_lang_ref_Reference.cc
index 524a18c..fc018d1 100644
--- a/runtime/native/java_lang_ref_Reference.cc
+++ b/runtime/native/java_lang_ref_Reference.cc
@@ -20,7 +20,7 @@
 
 #include "gc/heap.h"
 #include "gc/reference_processor.h"
-#include "jni_internal.h"
+#include "jni/jni_internal.h"
 #include "mirror/object-inl.h"
 #include "mirror/reference-inl.h"
 #include "native_util.h"