gpio: make of_get_named_gpiod_flags() private

of_get_named_gpiod_flags() is visible and directly usable by GPIO
consumers, but it really should not as the gpiod interface relies
on the simpler gpiod_get() to provide properly-configured GPIOs.

of_get_named_gpiod_flags() is just used internally by gpiolib to
implement gpiod_get(), and by the old of_get_named_gpio_flags()
function, therefore it makes sense to make it gpiolib-private.

As a side-effect, the unused (and unneeded) of_get_gpiod_flags()
inline function is also removed, and of_get_named_gpio_flags() is moved
from a static inline function to a regular one in gpiolib-of.c

This results in all references to gpiod_* functions in of_gpio.h being
gone, which is the way it should be since this file is part of the old
integer GPIO interface.

Changes since v1:
- Fixed compilation error when CONFIG_OF_GPIO is not defined
- Fixed warning due to of_gpio_flags enum not being declared
  in private gpiolib.h header

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.h

@@ -15,6 +15,8 @@
 #include <linux/err.h>
 #include <linux/device.h>
 
+enum of_gpio_flags;
+
 /**
  * struct acpi_gpio_info - ACPI GPIO specific information
  * @gpioint: if %true this GPIO is of type GpioInt otherwise type is GpioIo
@@ -46,4 +48,7 @@ acpi_get_gpiod_by_index(struct device *dev, int index,
 int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label);
 void gpiochip_free_own_desc(struct gpio_desc *desc);
 
+struct gpio_desc *of_get_named_gpiod_flags(struct device_node *np,
+		   const char *list_name, int index, enum of_gpio_flags *flags);
+
 #endif /* GPIOLIB_H */