add system sound audio context

bug: 27111558
Change-Id: Ifa08fc269afd021bae5239fc1e06aa9a7e75ecbc
diff --git a/include/hardware/vehicle.h b/include/hardware/vehicle.h
index bd623ab..71c57bc 100644
--- a/include/hardware/vehicle.h
+++ b/include/hardware/vehicle.h
@@ -729,6 +729,8 @@
     VEHICLE_AUDIO_CONTEXT_CD_ROM                         = 0x100,
     /** Aux audio input is played */
     VEHICLE_AUDIO_CONTEXT_AUX_AUDIO                      = 0x200,
+    /** system sound like UI feedback */
+    VEHICLE_AUDIO_CONTEXT_SYSTEM_SOUND                   = 0x400,
 };
 
 /**