fft-test: Remove possibility of returning restricted exit code

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavcodec/fft-test.c

@@ -489,5 +489,8 @@ int main(int argc, char **argv)
     av_free(tab_ref);
     av_free(exptab);
 
-    return err;
+    if (err)
+        printf("Error: %d.\n", err);
+
+    return !!err;
 }