crypto: sa2ul - Support for per channel coherency

crypto: sa2ul - Support for per channel coherency

On AM64 the DMA channel for sa2ul can be configured to be coherent or
non coherent via DT binding.

Use the dmaengine_get_device_for_dma_api() to get the device pointer which
should be used for with the dma_api to use matching dma_ops for the
channel coherency/non coherency.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vaibhav Gupta <v_gupta@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>