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>
int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2), void *arg, int *ret, int count, int size)
{
    int i;

    for (i = 0; i < count; i++) {
        int r = func(c, (char *)arg + i * size);
        if (ret)
            ret[i] = r;
    }
    emms_c();
    return 0;
}

int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2), void *arg, int *ret, int count, int size)
{
    int i;

    for (i = 0; i < count; i++) {
        int r = func(c, (char *)arg + i * size);
        if (ret)
            ret[i] = r;
    }
    emms_c();
    return 0;
}
