dmaengine: imx: Constify platform_device_id

The platform_device_id is not modified by the driver and core uses it as
const.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index eed4059..865501fc 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -193,7 +193,7 @@
 	int			 request;
 };
 
-static struct platform_device_id imx_dma_devtype[] = {
+static const struct platform_device_id imx_dma_devtype[] = {
 	{
 		.name = "imx1-dma",
 		.driver_data = IMX1_DMA,