vulkan: Unlock before return.

Fix defect reported by Coverity Scan CID-1494382.

Missing unlock (LOCK): Returning without unlocking queue->submit.mutex.

Fixes: 9bffd81f1c ("vulkan: Add common implementations of vkQueueSubmit and vkQueueWaitIdle")

Signed-off-by: Sergii Melikhov <sergii.v.melikhov@globallogic.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13933>

src/vulkan/runtime/vk_queue.c

@@ -463,6 +463,7 @@ vk_queue_submit_thread_func(void *_data)
       cnd_broadcast(&queue->submit.pop);
    }
 
+   mtx_unlock(&queue->submit.mutex);
    return 0;
 }