dma: ep93xx_dma: 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>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/ep93xx_dma.c

@@ -903,8 +903,7 @@ static int ep93xx_dma_alloc_chan_resources(struct dma_chan *chan)
 			switch (data->port) {
 			case EP93XX_DMA_SSP:
 			case EP93XX_DMA_IDE:
-				if (data->direction != DMA_MEM_TO_DEV &&
-				    data->direction != DMA_DEV_TO_MEM)
+				if (!is_slave_direction(data->direction))
 					return -EINVAL;
 				break;
 			default: