hal: add bus stream for front passenger zone

Add bus stream for front passenger zone playback
on automotive platform.

Primary zone         -> Mercury
Front passenger zone -> A2B1 (8CH DAC1) (ALL)
Rear seat zone       -> A2B2 (16CH DAC1&2) (SA81x5)
                        A2B1 (8CH DAC2) (SA6155)

Change-Id: Ib288f84c94d33f2f49d45b32d6810e0b91db967f
diff --git a/hal/audio_hw.c b/hal/audio_hw.c
index 8fc8770..5ddd193 100644
--- a/hal/audio_hw.c
+++ b/hal/audio_hw.c
@@ -410,6 +410,7 @@
     [USECASE_AUDIO_PLAYBACK_SYS_NOTIFICATION] = "sys-notification-playback",
     [USECASE_AUDIO_PLAYBACK_NAV_GUIDANCE] = "nav-guidance-playback",
     [USECASE_AUDIO_PLAYBACK_PHONE] = "phone-playback",
+    [USECASE_AUDIO_PLAYBACK_FRONT_PASSENGER] = "front-passenger-playback",
     [USECASE_AUDIO_PLAYBACK_REAR_SEAT] = "rear-seat-playback",
     [USECASE_AUDIO_FM_TUNER_EXT] = "fm-tuner-ext",
 };