Adding opus to list of audio formats

Adding opus to the list of audio formats enum.

This CL is part of adding Opus decoding support to android.

Change-Id: I41decf426ed3f76c10b27f247b1264010689c759
diff --git a/include/system/audio.h b/include/system/audio.h
index 2424baf..f662429 100644
--- a/include/system/audio.h
+++ b/include/system/audio.h
@@ -167,6 +167,7 @@
     AUDIO_FORMAT_HE_AAC_V1           = 0x05000000UL,
     AUDIO_FORMAT_HE_AAC_V2           = 0x06000000UL,
     AUDIO_FORMAT_VORBIS              = 0x07000000UL,
+    AUDIO_FORMAT_OPUS                = 0x08000000UL,
     AUDIO_FORMAT_MAIN_MASK           = 0xFF000000UL,
     AUDIO_FORMAT_SUB_MASK            = 0x00FFFFFFUL,