dmaengine: xilinx_dma: Add callback_result support

Take advantage of dmaengine_desc_get_callback_invoke which allows either
a callback or callback_result to be specified. This can be useful when
using the AXI DMA transfer unknown quantities of data where the residue
contained in the result can be used to calculate the number of bytes
transferred.

Signed-off-by: Nicholas Graumann <nick.graumann@gmail.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Link: https://lore.kernel.org/r/1571150904-3988-6-git-send-email-radhey.shyam.pandey@xilinx.com


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