tools/target_dec_fuzzer: check max samples in flush loop

Fixes: Timeout
Fixes: 36020/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-4774629855068160

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

tools/target_dec_fuzzer.c

@@ -441,6 +441,10 @@ maximums_reached:
         got_frame = 0;
         av_frame_unref(frame);
         decode_handler(ctx, frame, &got_frame, avpkt);
+
+        nb_samples += frame->nb_samples;
+        if (nb_samples > maxsamples)
+            break;
     } while (got_frame == 1 && it++ < maxiteration);
 
     fprintf(stderr, "pixels decoded: %"PRId64", samples decoded: %"PRId64", iterations: %d\n", ec_pixels, nb_samples, it);