vp8: Fix pthread_cond and pthread_mutex leaks

CC: libav-stable@libav.org
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/vp8.c

@@ -40,6 +40,10 @@ static void free_buffers(VP8Context *s)
     int i;
     if (s->thread_data)
         for (i = 0; i < MAX_THREADS; i++) {
+#if HAVE_THREADS
+            pthread_cond_destroy(&s->thread_data[i].cond);
+            pthread_mutex_destroy(&s->thread_data[i].lock);
+#endif
             av_freep(&s->thread_data[i].filter_strength);
             av_freep(&s->thread_data[i].edge_emu_buffer);
         }