venus: avoid feedback for external fence

Sync fd fence export implies a payload reset operation, and application
can immediately do another submission with the same fence after export.
Concurrent use of the same feedback slot is incorrect. Keeping a list of
feedback slots for sync_fd external fence is a bit over designed given
those fences are usually not checked or waited by the app, but will hand
off the ownership via sync fd to an external client.

Fixes: d7f2e6c8d0 ("venus: add fence feedback")

Signed-off-by: Yiwei Zhang <zzyiwei@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17975>
(cherry picked from commit 5457f4c0a4)

.pick_status.json

@@ -10903,7 +10903,7 @@
         "description": "venus: avoid feedback for external fence",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "d7f2e6c8d033de19a1d473df4fb1a46c7d365159"
     },

src/virtio/vulkan/vn_queue.c

@@ -538,6 +538,9 @@ vn_fence_feedback_init(struct vn_device *dev,
    VkCommandBuffer *cmd_handles;
    VkResult result;
 
+   if (fence->is_external)
+      return VK_SUCCESS;
+
    /* Fence feedback implementation relies on vkWaitForFences to cover the gap
     * between feedback slot signaling and the actual fence signal operation.
     */