extcon: palmas: Make of_device_id array const

Array of struct of_device_id may be be const as expected by
of_match_table field.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon-palmas.c

@@ -278,7 +278,7 @@ static int palmas_usb_resume(struct device *dev)
 
 static SIMPLE_DEV_PM_OPS(palmas_pm_ops, palmas_usb_suspend, palmas_usb_resume);
 
-static struct of_device_id of_palmas_match_tbl[] = {
+static const struct of_device_id of_palmas_match_tbl[] = {
 	{ .compatible = "ti,palmas-usb", },
 	{ .compatible = "ti,palmas-usb-vid", },
 	{ .compatible = "ti,twl6035-usb", },