dmaengine: at_xdmac: 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>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/at_xdmac.c

@@ -1572,8 +1572,8 @@ static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
 	desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc, xfer_node);
 	txd = &desc->tx_dma_desc;
 
-	if (txd->callback && (txd->flags & DMA_PREP_INTERRUPT))
-		txd->callback(txd->callback_param);
+	if (txd->flags & DMA_PREP_INTERRUPT)
+		dmaengine_desc_get_callback_invoke(txd, NULL);
 }
 
 static void at_xdmac_tasklet(unsigned long data)
@@ -1616,8 +1616,8 @@ static void at_xdmac_tasklet(unsigned long data)
 
 		if (!at_xdmac_chan_is_cyclic(atchan)) {
 			dma_cookie_complete(txd);
-			if (txd->callback && (txd->flags & DMA_PREP_INTERRUPT))
-				txd->callback(txd->callback_param);
+			if (txd->flags & DMA_PREP_INTERRUPT)
+				dmaengine_desc_get_callback_invoke(txd, NULL);
 		}
 
 		dma_run_dependencies(txd);