dmaengine: mpc512x_dma: convert callback to helper function

This is in preperation of moving to a callback that provides results to the
callback for the transaction. The conversion will maintain current behavior
and the driver must convert to new callback mechanism at a later time in
order to receive results.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/mpc512x_dma.c

@@ -411,8 +411,7 @@ static void mpc_dma_process_completed(struct mpc_dma *mdma)
 		list_for_each_entry(mdesc, &list, node) {
 			desc = &mdesc->desc;
 
-			if (desc->callback)
-				desc->callback(desc->callback_param);
+			dmaengine_desc_get_callback_invoke(desc, NULL);
 
 			last_cookie = desc->cookie;
 			dma_run_dependencies(desc);