Use DMB ST for store fence.

Change-Id: I4bde544a7c66e30a1756425ec088e53baa2f11a1
diff --git a/vm/mterp/armv7-a/platform.S b/vm/mterp/armv7-a/platform.S
index b9cdb07..5e6e837 100644
--- a/vm/mterp/armv7-a/platform.S
+++ b/vm/mterp/armv7-a/platform.S
@@ -54,7 +54,7 @@
  */
 .macro  SMP_DMB_ST
 #if ANDROID_SMP != 0
-    dmb                                 @ TODO: want "dmb st" here
+    dmb     st
 #else
     /* not SMP */
 #endif