Remove ALWAYS_INLINE from ReadBarrier::Mark().

This fixes a Ritzperf EAAC performance regression in the read barrier
config.

Bug: 26744236
Bug: 12687968
Change-Id: Ieaeb57def0e3a9eeb5fd8b1234658b45fd31ce77
diff --git a/runtime/read_barrier.h b/runtime/read_barrier.h
index 3169a8b..77be6cf 100644
--- a/runtime/read_barrier.h
+++ b/runtime/read_barrier.h
@@ -80,8 +80,7 @@
   static void AssertToSpaceInvariant(GcRootSource* gc_root_source, mirror::Object* ref)
       SHARED_REQUIRES(Locks::mutator_lock_);
 
-  ALWAYS_INLINE static mirror::Object* Mark(mirror::Object* obj)
-      SHARED_REQUIRES(Locks::mutator_lock_);
+  static mirror::Object* Mark(mirror::Object* obj) SHARED_REQUIRES(Locks::mutator_lock_);
 
   static mirror::Object* WhitePtr() {
     return reinterpret_cast<mirror::Object*>(white_ptr_);