gpio: make gpiochip_get_desc() gpiolib-private

As GPIO descriptors are not going to remain unique anymore, having this
function public is not safe. Restrain its use to gpiolib since we have
no user outside of it.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 98020c3..acbb933 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -51,6 +51,8 @@
 struct gpio_desc *of_get_named_gpiod_flags(struct device_node *np,
 		   const char *list_name, int index, enum of_gpio_flags *flags);
 
+struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip, u16 hwnum);
+
 extern struct spinlock gpio_lock;
 extern struct list_head gpio_chips;