Enable multi-format USB audio playback for Manta

Change-Id: Id0181c68f5bef8aa98c256d41190782ffd9bc8ea
diff --git a/audio_policy.conf b/audio_policy.conf
index 0414cb7..3063575 100644
--- a/audio_policy.conf
+++ b/audio_policy.conf
@@ -74,7 +74,7 @@
       usb_device {
         sampling_rates dynamic
         channel_masks AUDIO_CHANNEL_OUT_STEREO
-        formats AUDIO_FORMAT_PCM_16_BIT
+        formats dynamic
         devices AUDIO_DEVICE_OUT_USB_DEVICE
       }
     }