Use dmaenginem_async_device_register to simplify the code:
	remove dma_async_device_unregister.
Signed-off-by: Huang Shijie <sjhuang@iluvatar.ai>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Vinod Koul <vkoul@kernel.org>