iio: adc: ad7768-1: use static for local functions

All of the gpio functions are not exported or meant to be user by
another source file or driver. Therefore define them as static.

This was spotted when preparing a 6.12 RPI branch as we'll start getting
warnings regarding this. So better fix it now.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>

Author: nunojsa

drivers/iio/adc/ad7768-1.c

@@ -378,7 +378,7 @@ static int ad7768_set_dig_fil(struct ad7768_state *st,
 	return 0;
 }
 
-int ad7768_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
+static int ad7768_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
 {
 	struct ad7768_state *st = gpiochip_get_data(chip);
 	int ret;
@@ -393,8 +393,8 @@ int ad7768_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
 	return ret;
 }
 
-int ad7768_gpio_direction_output(struct gpio_chip *chip,
-				 unsigned int offset, int value)
+static int ad7768_gpio_direction_output(struct gpio_chip *chip,
+					unsigned int offset, int value)
 {
 	struct ad7768_state *st = gpiochip_get_data(chip);
 	int ret;
@@ -409,7 +409,7 @@ int ad7768_gpio_direction_output(struct gpio_chip *chip,
 	return ret;
 }
 
-int ad7768_gpio_get(struct gpio_chip *chip, unsigned int offset)
+static int ad7768_gpio_get(struct gpio_chip *chip, unsigned int offset)
 {
 	struct ad7768_state *st = gpiochip_get_data(chip);
 	unsigned int val;
@@ -435,7 +435,7 @@ int ad7768_gpio_get(struct gpio_chip *chip, unsigned int offset)
 	return ret;
 }
 
-void ad7768_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
+static void ad7768_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
 {
 	struct ad7768_state *st = gpiochip_get_data(chip);
 	unsigned int val;
@@ -456,7 +456,7 @@ void ad7768_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
 	mutex_unlock(&st->lock);
 }
 
-int ad7768_gpio_request(struct gpio_chip *chip, unsigned int offset)
+static int ad7768_gpio_request(struct gpio_chip *chip, unsigned int offset)
 {
 	struct ad7768_state *st = gpiochip_get_data(chip);
 
@@ -468,7 +468,7 @@ int ad7768_gpio_request(struct gpio_chip *chip, unsigned int offset)
 	return 0;
 }
 
-int ad7768_gpio_init(struct ad7768_state *st)
+static int ad7768_gpio_init(struct ad7768_state *st)
 {
 	int ret;