dmaengine: at_xdmac: Replace two if statements with only one with two conditions

Add a cosmetic change and replace two if statements with a single if
statement with two conditions. In case the optional txstate parameter is
NULL, we return the dma_cookie_status, which is fine, no functional change
required.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20220802140630.243550-1-tudor.ambarus@microchip.com


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