turnip: Close sync_fd only if it is a valid file descriptor.

Fix defects reported by Coverity Scan.

Argument cannot be negative (NEGATIVE_RETURNS)
negative_returns: sync_fd is passed to a parameter that cannot be negative.

Fixes: cec0bc73e5 ("turnip: rework fences to use syncobjs")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7647>

src/freedreno/vulkan/tu_wsi_display.c

@@ -282,12 +282,12 @@ tu_RegisterDeviceEventEXT(VkDevice                    _device,
                                       allocator,
                                       NULL,
                                       sync_fd);
+
+      close(sync_fd);
    } else {
       ret = VK_ERROR_OUT_OF_HOST_MEMORY;
    }
 
-   close(sync_fd);
-
    if (ret != VK_SUCCESS)
       tu_DestroyFence(_device, *_fence, allocator);
 
@@ -319,12 +319,12 @@ tu_RegisterDisplayEventEXT(VkDevice                           _device,
                                        allocator,
                                        NULL,
                                        sync_fd);
+
+      close(sync_fd);
    } else {
       ret = VK_ERROR_OUT_OF_HOST_MEMORY;
    }
 
-   close(sync_fd);
-
    if (ret != VK_SUCCESS)
       tu_DestroyFence(_device, *_fence, allocator);