hal: Add support for audio-hal-plugin silent mode messages

* Add silent mode message types
* Set silent boot feature flag

Signed-off-by: Tahir Dawson <dawson@codeaurora.org>
Change-Id: I4c0a772affb0b7001192bf1bdc5aa0e2d4da711b
diff --git a/hal/audio_hal_plugin.h b/hal/audio_hal_plugin.h
index b5033c8..3d77b23 100644
--- a/hal/audio_hal_plugin.h
+++ b/hal/audio_hal_plugin.h
@@ -86,6 +86,7 @@
     AUDIO_HAL_PLUGIN_MSG_CODEC_GET_PP_EQ, /**< get EQ params */
     AUDIO_HAL_PLUGIN_MSG_CODEC_GET_PP_EQ_SUBBANDS, /**< get EQ subbands params */
     AUDIO_HAL_PLUGIN_MSG_CODEC_TUNNEL_GET_CMD, /**< pass through get cmds */
+    AUDIO_HAL_PLUGIN_MSG_SILENT_MODE, /**<set silent boot mode */
     AUDIO_HAL_PLUGIN_MSG_MAX
 } audio_hal_plugin_msg_type_t;