audio policy: register effect CPU on enable

Added a method on audio policy interface to register
audio effect CPU usage on enable and unregister on disable
instead of when the effect is created or destroyed.

Change-Id: Iee20bf70fee7302f817ec4c7d9bf7640caca2e95
diff --git a/include/hardware/audio_policy.h b/include/hardware/audio_policy.h
index d0d7979..fc56e5e 100644
--- a/include/hardware/audio_policy.h
+++ b/include/hardware/audio_policy.h
@@ -212,6 +212,8 @@
 
     int (*unregister_effect)(struct audio_policy *pol, int id);
 
+    int (*set_effect_enabled)(struct audio_policy *pol, int id, bool enabled);
+
     bool (*is_stream_active)(const struct audio_policy *pol,
                              int stream,
                              uint32_t in_past_ms);