hal: add rear seat playback support for automotive

Add rear seat playback support for multi-zone
audio support on automotive platform.

Change-Id: Ia3d4c4a4f78950e99a8d4955e910cc8902b6bb17
diff --git a/hal/audio_extn/utils.c b/hal/audio_extn/utils.c
index fe368e9..a29b6e5 100644
--- a/hal/audio_extn/utils.c
+++ b/hal/audio_extn/utils.c
@@ -150,6 +150,7 @@
     STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_SYS_NOTIFICATION),
     STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_NAV_GUIDANCE),
     STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_PHONE),
+    STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_REAR_SEAT),
     STRING_TO_ENUM(AUDIO_INPUT_FLAG_NONE),
     STRING_TO_ENUM(AUDIO_INPUT_FLAG_FAST),
     STRING_TO_ENUM(AUDIO_INPUT_FLAG_HW_HOTWORD),