avcodec/ffv1dec_template: Optimize golomb run mode

Fixes: Timeout (34sec -> 12sec)
Fixes: 13398/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFV1_fuzzer-5664106709778432

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/ffv1dec_template.c

@@ -86,6 +86,11 @@ static av_always_inline int RENAME(decode_line)(FFV1Context *s, int w,
                         run_mode = 2;
                     }
                 }
+                while (run_count > 1 && w-x > 1) {
+                    sample[1][x] = RENAME(predict)(sample[1] + x, sample[0] + x);
+                    x++;
+                    run_count--;
+                }
                 run_count--;
                 if (run_count < 0) {
                     run_mode  = 0;