hal: add support for ull audio playback

- Add a new use case and mixer paths to support ultra
  low latency audio playback.
  This use case exercises the ULL mode in the DSP.

CRs-Fixed: 889183
Change-Id: I6685dd0f346072029ca51e4ce92856a13e74ee76
diff --git a/hal/msm8916/platform.c b/hal/msm8916/platform.c
index 6592c35..934850f 100644
--- a/hal/msm8916/platform.c
+++ b/hal/msm8916/platform.c
@@ -281,6 +281,7 @@
     [USECASE_AUDIO_PLAYBACK_OFFLOAD8] = {-1, -1},
     [USECASE_AUDIO_PLAYBACK_OFFLOAD9] = {-1, -1},
 #endif
+    [USECASE_AUDIO_PLAYBACK_ULL] = {MULTIMEDIA3_PCM_DEVICE, MULTIMEDIA3_PCM_DEVICE},
     [USECASE_AUDIO_RECORD] = {AUDIO_RECORD_PCM_DEVICE, AUDIO_RECORD_PCM_DEVICE},
     [USECASE_AUDIO_RECORD_COMPRESS] = {COMPRESS_CAPTURE_DEVICE, COMPRESS_CAPTURE_DEVICE},
     [USECASE_AUDIO_RECORD_LOW_LATENCY] = {LOWLATENCY_PCM_DEVICE,
@@ -664,6 +665,7 @@
     {TO_NAME_INDEX(USECASE_AUDIO_PLAYBACK_OFFLOAD8)},
     {TO_NAME_INDEX(USECASE_AUDIO_PLAYBACK_OFFLOAD9)},
 #endif
+    {TO_NAME_INDEX(USECASE_AUDIO_PLAYBACK_ULL)},
     {TO_NAME_INDEX(USECASE_AUDIO_RECORD)},
     {TO_NAME_INDEX(USECASE_AUDIO_RECORD_LOW_LATENCY)},
     {TO_NAME_INDEX(USECASE_VOICE_CALL)},