dmaengine: xilinx_dma: Set dma_device directions

dmaengine: xilinx_dma: Set dma_device directions

Coalesce the direction bits from the enabled TX and/or RX channels into
the directions bit mask of dma_device. Without this mask set,
dma_get_slave_caps() in the DMAEngine fails, which prevents the driver
from being used with an IIO DMAEngine buffer.

Signed-off-by: Thomas Gessler <thomas.gessler@brueckmann-gmbh.de>
Reviewed-by: Suraj Gupta <suraj.gupta2@amd.com>
Tested-by: Folker Schwesinger <dev@folker-schwesinger.de>
Link: https://lore.kernel.org/r/20250507182101.909010-1-thomas.gessler@brueckmann-gmbh.de
Signed-off-by: Vinod Koul <vkoul@kernel.org>