dmaengine: xilinx_dma: fix mixed_enum_type coverity warning

Typecast the fls(width -1) with (enum dmaengine_alignment) in
xilinx_dma_chan_probe function to fix the coverity warning.

Addresses-Coverity: Event mixed_enum_type.
Fixes: 9cd4360d

 ("dma: Add Xilinx AXI Video Direct Memory Access Engine driver support")
Signed-off-by: Shravya Kumbham <shravya.kumbham@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Link: https://lore.kernel.org/r/1608722462-29519-4-git-send-email-radhey.shyam.pandey@xilinx.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>