audio policy: add device for audio bus

Add audio device category representing a bus in the
audio subsystem. E.g a set of channels in MOST automotive bus.

Bug: 25448664
Change-Id: Id00da57dc45037d4d8062e9a747c423940611539
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 4807400..18592f1 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -468,6 +468,7 @@
         {AUDIO_DEVICE_OUT_AUX_LINE,         "AUX_LINE"},
         {AUDIO_DEVICE_OUT_SPEAKER_SAFE,     "SPEAKER_SAFE"},
         {AUDIO_DEVICE_OUT_IP,               "IP"},
+        {AUDIO_DEVICE_OUT_BUS,              "BUS"},
         {AUDIO_DEVICE_NONE,                 "NONE"},       // must be last
     }, mappingsIn[] = {
         {AUDIO_DEVICE_IN_COMMUNICATION,     "COMMUNICATION"},
@@ -491,6 +492,7 @@
         {AUDIO_DEVICE_IN_BLUETOOTH_A2DP,    "BLUETOOTH_A2DP"},
         {AUDIO_DEVICE_IN_LOOPBACK,          "LOOPBACK"},
         {AUDIO_DEVICE_IN_IP,                "IP"},
+        {AUDIO_DEVICE_IN_BUS,               "BUS"},
         {AUDIO_DEVICE_NONE,                 "NONE"},        // must be last
     };
     String8 result;