hwdec_cuda: clear vulkan semaphore fd after passing ownership to cuda

This is not technically necessary, because we never touch the fd again
after passing to cuda, but having it there could lead to future code
accidentally using it.

video/out/hwdec/hwdec_cuda_vk.c

@@ -176,6 +176,7 @@ static bool cuda_ext_vk_init(struct ra_hwdec_mapper *mapper,
     if (ret < 0)
         goto error;
     // CUDA takes ownership of an imported FD *but not* an imported Handle.
+    evk->sem_handle.fd = -1;
 #else
     evk->sync = pl_sync_create(gpu, HANDLE_TYPE);
     if (!evk->sync) {