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>
diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
index 7ebcf9b..5358453 100644
--- a/drivers/dma/sun6i-dma.c
+++ b/drivers/dma/sun6i-dma.c
@@ -896,7 +896,7 @@
 	.nr_max_vchans   = 37,
 };
 
-static struct of_device_id sun6i_dma_match[] = {
+static const struct of_device_id sun6i_dma_match[] = {
 	{ .compatible = "allwinner,sun6i-a31-dma", .data = &sun6i_a31_dma_cfg },
 	{ .compatible = "allwinner,sun8i-a23-dma", .data = &sun8i_a23_dma_cfg },
 	{ /* sentinel */ }