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-of.c

@@ -96,6 +96,20 @@ struct gpio_desc *of_get_named_gpiod_flags(struct device_node *np,
 }
 EXPORT_SYMBOL(of_get_named_gpiod_flags);
 
+int of_get_named_gpio_flags(struct device_node *np, const char *list_name,
+			    int index, enum of_gpio_flags *flags)
+{
+	struct gpio_desc *desc;
+
+	desc = of_get_named_gpiod_flags(np, list_name, index, flags);
+
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+	else
+		return desc_to_gpio(desc);
+}
+EXPORT_SYMBOL(of_get_named_gpio_flags);
+
 /**
  * of_gpio_simple_xlate - translate gpio_spec to the GPIO number and flags
  * @gc:		pointer to the gpio_chip structure