netdev: octeon_mgmt: 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: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/octeon/octeon_mgmt.c

@@ -1557,7 +1557,7 @@ static int octeon_mgmt_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static struct of_device_id octeon_mgmt_match[] = {
+static const struct of_device_id octeon_mgmt_match[] = {
 	{
 		.compatible = "cavium,octeon-5750-mix",
 	},