dma: ipu_idmac: reuse is_slave_direction helper

The is_slave_direction helps to check if the transfer type is slave.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/ipu/ipu_idmac.c

@@ -1347,7 +1347,7 @@ static struct dma_async_tx_descriptor *idmac_prep_slave_sg(struct dma_chan *chan
 	    chan->chan_id != IDMAC_IC_7)
 		return NULL;
 
-	if (direction != DMA_DEV_TO_MEM && direction != DMA_MEM_TO_DEV) {
+	if (!is_slave_direction(direction)) {
 		dev_err(chan->device->dev, "Invalid DMA direction %d!\n", direction);
 		return NULL;
 	}