dmaengine: at_xdmac: Fix at_xdmac_lld struct definition

The hardware channel next descriptor view structure contains just
fields of 32 bits, while dma_addr_t can be of type u64 or u32
depending on CONFIG_ARCH_DMA_ADDR_T_64BIT. Force u32 to comply with
what the hardware expects.

Fixes: e1f7c9ee

 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20211215110115.191749-11-tudor.ambarus@microchip.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>