dmaengine: at_hdmac: Drop description for a not defined parameter

Probably a leftover, drop it.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Link: https://lore.kernel.org/r/20200123140237.125799-4-tudor.ambarus@microchip.com


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