dmaengine: mmp_tdma: 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/mmp_tdma.c

@@ -349,9 +349,7 @@ static void dma_do_tasklet(unsigned long data)
 {
 	struct mmp_tdma_chan *tdmac = (struct mmp_tdma_chan *)data;
 
-	if (tdmac->desc.callback)
-		tdmac->desc.callback(tdmac->desc.callback_param);
-
+	dmaengine_desc_get_callback_invoke(&tdmac->desc, NULL);
 }
 
 static void mmp_tdma_free_descriptor(struct mmp_tdma_chan *tdmac)