ART: Move to using locks.h instead of mutex.h

When only annotating lock requirements, use locks.h.

Bug: 119869270
Test: mmma art
Change-Id: I1608b03254712feff0072ebad012c3af0cc3dda4
diff --git a/runtime/class_linker.h b/runtime/class_linker.h
index dd5f911..d3eab7c 100644
--- a/runtime/class_linker.h
+++ b/runtime/class_linker.h
@@ -25,8 +25,8 @@
 #include <vector>
 
 #include "base/enums.h"
+#include "base/locks.h"
 #include "base/macros.h"
-#include "base/mutex.h"
 #include "dex/class_accessor.h"
 #include "dex/dex_cache_resolved_classes.h"
 #include "dex/dex_file.h"