pinctrl: Declare operation structures as const

The pinconf, pinctrl and pinmux operation structures hold function
pointers that are never modified. Declare them as const.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/pinctrl-xway.c b/drivers/pinctrl/pinctrl-xway.c
index 068224e..f2977cf 100644
--- a/drivers/pinctrl/pinctrl-xway.c
+++ b/drivers/pinctrl/pinctrl-xway.c
@@ -553,7 +553,7 @@
 	return ret;
 }
 
-static struct pinconf_ops xway_pinconf_ops = {
+static const struct pinconf_ops xway_pinconf_ops = {
 	.pin_config_get	= xway_pinconf_get,
 	.pin_config_set	= xway_pinconf_set,
 	.pin_config_group_set = xway_pinconf_group_set,