dmaengine: axi-dmac: check cache coherency register

Marking the DMA as cache coherent (dma-coherent in devicetree) is only
safe with versions of axi_dmac that have this feature enabled.

Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Vinod Koul <vkoul@kernel.org>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Mathias Tausen <mta@satlab.com>
Link: https://lore.kernel.org/r/20220726140213.786939-1-mta@satlab.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>