dmaengine: fsl-edma: support edma memcpy

Add memcpy in edma. The edma has the capability to transfer data by
software trigger so that it could be used for memory copy. Enable
MEMCPY for edma driver and it could be test directly by dmatest.

Signed-off-by: Joy Zou <joy.zou@nxp.com>
Link: https://lore.kernel.org/r/20211026090025.2777292-1-joy.zou@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>