audio policy: add forced uses for system

The volume and routing policy of AUDIO_STREAM_ENFORCED_AUDIBLE is
now controlled by AudioService by means of new forced use type
AUDIO_POLICY_FORCE_FOR_SYSTEM with config
AUDIO_POLICY_FORCE_SYSTEM_ENFORCED.

Bug 7032634.

Change-Id: Ib1834ec507f3aa726895b8fd3e8a91cc9cc601a7
diff --git a/include/system/audio_policy.h b/include/system/audio_policy.h
index 7b82d8d..6b49a80 100644
--- a/include/system/audio_policy.h
+++ b/include/system/audio_policy.h
@@ -44,6 +44,7 @@
     AUDIO_POLICY_FORCE_DIGITAL_DOCK,
     AUDIO_POLICY_FORCE_NO_BT_A2DP, /* A2DP sink is not preferred to speaker or wired HS */
     AUDIO_POLICY_FORCE_REMOTE_SUBMIX,
+    AUDIO_POLICY_FORCE_SYSTEM_ENFORCED,
 
     AUDIO_POLICY_FORCE_CFG_CNT,
     AUDIO_POLICY_FORCE_CFG_MAX = AUDIO_POLICY_FORCE_CFG_CNT - 1,
@@ -57,6 +58,7 @@
     AUDIO_POLICY_FORCE_FOR_MEDIA,
     AUDIO_POLICY_FORCE_FOR_RECORD,
     AUDIO_POLICY_FORCE_FOR_DOCK,
+    AUDIO_POLICY_FORCE_FOR_SYSTEM,
 
     AUDIO_POLICY_FORCE_USE_CNT,
     AUDIO_POLICY_FORCE_USE_MAX = AUDIO_POLICY_FORCE_USE_CNT - 1,