Mount schedTune cgroup as /dev/stune

Make stune consistent with the other cgroups mounted under /dev

Change-Id: I0fe7120ad2afbe8e6a3c9f72cc3f465de618d344
diff --git a/libcutils/sched_policy.c b/libcutils/sched_policy.c
index 54d1122..e56af57 100644
--- a/libcutils/sched_policy.c
+++ b/libcutils/sched_policy.c
@@ -138,9 +138,9 @@
         ta_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
 
 #ifdef USE_SCHEDBOOST
-        filename = "/sys/fs/cgroup/stune/foreground/tasks";
+        filename = "/dev/stune/foreground/tasks";
         fg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
-        filename = "/sys/fs/cgroup/stune/tasks";
+        filename = "/dev/stune/tasks";
         bg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
 #endif
     }