Add audio/eac3-joc to FFmpeg supported formats

If compiled with eac3, audio/eac3-joc stream 5.1 bed-channels
can be decoded. The stream will be decoded as 2-D rather than
3-D.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=206296930

extensions/ffmpeg/src/main/java/com/google/android/exoplayer2/ext/ffmpeg/FfmpegLibrary.java

@@ -87,6 +87,7 @@ public final class FfmpegLibrary {
       case MimeTypes.AUDIO_AC3:
         return "ac3";
       case MimeTypes.AUDIO_E_AC3:
+      case MimeTypes.AUDIO_E_AC3_JOC:
         return "eac3";
       case MimeTypes.AUDIO_TRUEHD:
         return "truehd";