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/include/linux/pinctrl/pinctrl.h b/include/linux/pinctrl/pinctrl.h
index 778804d..2c2a9e8 100644
--- a/include/linux/pinctrl/pinctrl.h
+++ b/include/linux/pinctrl/pinctrl.h
@@ -118,9 +118,9 @@
 	const char *name;
 	struct pinctrl_pin_desc const *pins;
 	unsigned int npins;
-	struct pinctrl_ops *pctlops;
-	struct pinmux_ops *pmxops;
-	struct pinconf_ops *confops;
+	const struct pinctrl_ops *pctlops;
+	const struct pinmux_ops *pmxops;
+	const struct pinconf_ops *confops;
 	struct module *owner;
 };