dmaengine: constify of_device_id array

of_device_id is always used as const.
(See driver.of_match_table and open firmware functions)

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/mmp_pdma.c

@@ -970,7 +970,7 @@ static int mmp_pdma_chan_init(struct mmp_pdma_device *pdev, int idx, int irq)
 	return 0;
 }
 
-static struct of_device_id mmp_pdma_dt_ids[] = {
+static const struct of_device_id mmp_pdma_dt_ids[] = {
 	{ .compatible = "marvell,pdma-1.0", },
 	{}
 };