spi: spi-fsl-dspi: constify devtype_data

of_id->data is const, so instead of casting the pointer to drop its
const status, this patch constify the devtype_data pointer.
Signed-off-by: LABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-dspi.c

@@ -159,7 +159,7 @@ struct fsl_dspi {
 	u8			cs;
 	u16			void_write_data;
 	u32			cs_change;
-	struct fsl_dspi_devtype_data *devtype_data;
+	const struct fsl_dspi_devtype_data *devtype_data;
 
 	wait_queue_head_t	waitq;
 	u32			waitflags;
@@ -686,7 +686,7 @@ static int dspi_probe(struct platform_device *pdev)
 	}
 	master->bus_num = bus_num;
 
-	dspi->devtype_data = (struct fsl_dspi_devtype_data *)of_id->data;
+	dspi->devtype_data = of_id->data;
 	if (!dspi->devtype_data) {
 		dev_err(&pdev->dev, "can't get devtype_data\n");
 		ret = -EFAULT;