dmaengine: imx-sdma: 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/imx-sdma.c

@@ -650,8 +650,7 @@ static void sdma_event_disable(struct sdma_channel *sdmac, unsigned int event)
 
 static void sdma_handle_channel_loop(struct sdma_channel *sdmac)
 {
-	if (sdmac->desc.callback)
-		sdmac->desc.callback(sdmac->desc.callback_param);
+	dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL);
 }
 
 static void sdma_update_channel_loop(struct sdma_channel *sdmac)
@@ -701,8 +700,8 @@ static void mxc_sdma_handle_channel_normal(struct sdma_channel *sdmac)
 		sdmac->status = DMA_COMPLETE;
 
 	dma_cookie_complete(&sdmac->desc);
-	if (sdmac->desc.callback)
-		sdmac->desc.callback(sdmac->desc.callback_param);
+
+	dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL);
 }
 
 static void sdma_tasklet(unsigned long data)