audio: add key to control AANC runtime

- add AANC key to enable\disable AANC runtime

Bug: 29111687

Change-Id: I5c64b190b336a834cf6793ed37a511a54c7a202e
diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index ec7fd4b..3b734f7 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -147,6 +147,9 @@
 /* Enable mono audio playback if 1, else should be 0. */
 #define AUDIO_PARAMETER_MONO_OUTPUT "mono_output"
 
+/* Enable AANC */
+#define AUDIO_PARAMETER_KEY_AANC "aanc_enabled"
+
 /**
  * audio codec parameters
  */