mfd: tps6586x: Make of_device_id array const

Make of_device_id array const, because all OF functions
handle it as const.

Signed-off-by: Jingoo Han <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/tps6586x.c

···
 	return pdata;
 }
 
-static struct of_device_id tps6586x_of_match[] = {
+static const struct of_device_id tps6586x_of_match[] = {
 	{ .compatible = "ti,tps6586x", },
 	{ },
 };