dmaengine: axi-dmac: assign `copy_align` property

The `copy_align` property is a generic property that describes alignment
for DMA memcpy & sg ops.
It serves mostly an informational purpose, and can be used in DMA tests, to
pass the info to know what alignment to expect.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>