audio: add parameter for device shutdown notification

 - Add new define to receive device shutdown notification

Change-Id: I387b40af5119fa43d2e36e3ee19cbca526e49c2a
diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index 2389c09..ca7b18b 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -117,6 +117,9 @@
  * or no HW sync is available. */
 #define AUDIO_PARAMETER_HW_AV_SYNC "hw_av_sync"
 
+/* Device state*/
+#define AUDIO_PARAMETER_KEY_DEV_SHUTDOWN "dev_shutdown"
+
 /**
  *  audio stream parameters
  */