dmaengine: xilinx: Fix module autoload for OF platform driver

This platform driver has a OF device ID table but the OF module
alias information is not created so module autoloading won't work.

Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>