avcodec/utils: correct align value for interplay

Fixes out of array access
Fixes: 452/fuzz-1-ffmpeg_VIDEO_AV_CODEC_ID_INTERPLAY_VIDEO_fuzzer

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
AVCodec *av_codec_next(const AVCodec *c)
{
    if (c)
        return c->next;
    else
        return first_avcodec;
}

AVCodec *av_codec_next(const AVCodec *c)
{
    if (c)
        return c->next;
    else
        return first_avcodec;
}
