gpiolib: of: constify few local device_node variables

gpiolib does not modify struct device_node, so few local pointers can
point to a const data.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpiolib-of.c

@@ -122,7 +122,7 @@ static struct gpio_desc *of_xlate_and_get_gpiod_flags(struct gpio_chip *chip,
 bool of_gpio_need_valid_mask(const struct gpio_chip *gc)
 {
 	int size;
-	struct device_node *np = gc->of_node;
+	const struct device_node *np = gc->of_node;
 
 	size = of_property_count_u32_elems(np,  "gpio-reserved-ranges");
 	if (size > 0 && size % 2 == 0)
@@ -373,7 +373,7 @@ static struct gpio_desc *of_find_spi_gpio(struct device *dev, const char *con_id
 					  enum of_gpio_flags *of_flags)
 {
 	char prop_name[32]; /* 32 is max size of property name */
-	struct device_node *np = dev->of_node;
+	const struct device_node *np = dev->of_node;
 	struct gpio_desc *desc;
 
 	/*
@@ -404,7 +404,7 @@ static struct gpio_desc *of_find_spi_cs_gpio(struct device *dev,
 					     unsigned int idx,
 					     unsigned long *flags)
 {
-	struct device_node *np = dev->of_node;
+	const struct device_node *np = dev->of_node;
 
 	if (!IS_ENABLED(CONFIG_SPI_MASTER))
 		return ERR_PTR(-ENOENT);
@@ -440,7 +440,7 @@ static struct gpio_desc *of_find_regulator_gpio(struct device *dev, const char *
 		"wlf,ldo1ena", /* WM8994 */
 		"wlf,ldo2ena", /* WM8994 */
 	};
-	struct device_node *np = dev->of_node;
+	const struct device_node *np = dev->of_node;
 	struct gpio_desc *desc;
 	int i;