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.h b/hal/audio_hw.h
index 5e3c1cb..7969c22 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -240,6 +240,7 @@
     USECASE_AUDIO_PLAYBACK_SYS_NOTIFICATION,
     USECASE_AUDIO_PLAYBACK_NAV_GUIDANCE,
     USECASE_AUDIO_PLAYBACK_PHONE,
+    USECASE_AUDIO_PLAYBACK_FRONT_PASSENGER,
     USECASE_AUDIO_PLAYBACK_REAR_SEAT,
 
     /*Audio FM Tuner usecase*/
@@ -312,18 +313,22 @@
     RENDER_MODE_AUDIO_STC_MASTER,
 } render_mode_t;
 
-/* This defines the physical car streams supported in audio HAL,
- * limited by the available frontend PCM driver.
- * Max number of physical streams supported is currently 16 and is
+/* This defines the physical car audio streams supported in
+ * audio HAL, limited by the available frontend PCM devices.
+ * Max number of physical streams supported is 32 and is
  * represented by stream bit flag.
+ *     Primary zone: bit 0 - 7
+ *     Front passenger zone: bit 8 - 15
+ *     Rear seat zone: bit 16 - 23
  */
-#define MAX_CAR_AUDIO_STREAMS    16
+#define MAX_CAR_AUDIO_STREAMS    32
 enum {
     CAR_AUDIO_STREAM_MEDIA            = 0x1,
     CAR_AUDIO_STREAM_SYS_NOTIFICATION = 0x2,
     CAR_AUDIO_STREAM_NAV_GUIDANCE     = 0x4,
     CAR_AUDIO_STREAM_PHONE            = 0x8,
-    CAR_AUDIO_STREAM_REAR_SEAT        = 0x100,
+    CAR_AUDIO_STREAM_FRONT_PASSENGER  = 0x100,
+    CAR_AUDIO_STREAM_REAR_SEAT        = 0x10000,
 };
 
 struct stream_app_type_cfg {