player/video: avoid spamming logs with EOF

When playing a sparse video stream, the debug log gets hit with the
video EOF constantly since the audio is still playing. There's no
practical use for this so just do add some logic to only signal it once
if it is sparse.

player/core.h

@@ -168,6 +168,7 @@ struct vo_chain {
     bool is_coverart;
     // - video consists of sparse still images
     bool is_sparse;
+    bool sparse_eof_signalled;
 
     bool underrun;
     bool underrun_signaled;

player/video.c

@@ -1097,7 +1097,11 @@ void write_video(struct MPContext *mpctx)
             }
         }
 
+        // Avoid pointlessly spamming the logs every frame.
+        if (!vo_c->is_sparse || !vo_c->sparse_eof_signalled) {
             MP_DBG(mpctx, "video EOF (status=%d)\n", mpctx->video_status);
+            vo_c->sparse_eof_signalled = vo_c->is_sparse;
+        }
         return;
     }