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 <[e-mail]>
Reviewed-by: Viresh Kumar <[e-mail]>
Acked-by: Mika Westerberg <[e-mail]>
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/ep93xx_dma.c

···
 			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: