thermosphere: add proper memory/instruction barriers for breakpoint stuff

thermosphere/src/watchpoints.c

@@ -56,6 +56,7 @@ static void commitAndBroadcastWatchpointHandler(void *p)
 
 static inline void commitAndBroadcastWatchpoints(void)
 {
+    __dmb_sy();
     executeFunctionOnAllCores(commitAndBroadcastWatchpointHandler, NULL, true);
 }
 
@@ -331,4 +332,4 @@ int removeAllWatchpoints(void)
     recursiveSpinlockUnlock(&g_watchpointManager.lock);
 
     return 0;
-}
+}