freedreno: unref old fence

Some, but not all, state trackers will explicitly unref (and set to
NULL) the previous *fence before calling pipe->flush().  So driver
should use fence_ref() which will unref the old fence if not NULL.

Signed-off-by: Rob Clark <robclark@freedesktop.org>

src/gallium/drivers/freedreno/freedreno_context.c

@@ -144,8 +144,10 @@ fd_context_flush(struct pipe_context *pctx, struct pipe_fence_handle **fence,
 {
 	fd_context_render(pctx);
 
-	if (fence)
+	if (fence) {
+		fd_screen_fence_ref(pctx->screen, fence, NULL);
 		*fence = fd_fence_create(pctx);
+	}
 }
 
 void