task_profiles.json: use system subgroup for NormalPerformance

Put tasks into a subgroup so that we can set things up e.g. soft cpu
bandwidth and/or uclamp.

Bug: 170507876
Bug: 171740453
Test: boot and check cgroup
Change-Id: Iaeb081bc4f214aa23eb281e0c28a81ea581bb4d1
diff --git a/libprocessgroup/profiles/task_profiles.json b/libprocessgroup/profiles/task_profiles.json
index ea0064f..b528fa5 100644
--- a/libprocessgroup/profiles/task_profiles.json
+++ b/libprocessgroup/profiles/task_profiles.json
@@ -100,7 +100,7 @@
           "Params":
           {
             "Controller": "cpu",
-            "Path": ""
+            "Path": "system"
           }
         }
       ]