dmaengine: xilinx_dma: Set max segment size

Set the maximumg DMA segment size from the actual core configuration
value. Without this setting, the default value of 64 KiB is reported,
and larger sizes cannot be used for IIO DMAEngine buffers.

Signed-off-by: Thomas Gessler <thomas.gessler@brueckmann-gmbh.de>
Tested-by: Folker Schwesinger <dev@folker-schwesinger.de>
Link: https://lore.kernel.org/r/20250314134717.703287-1-thomas.gessler@brueckmann-gmbh.de


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