gpio: add ops to set dir flags

Add the ops for GPIO driver set_dir_flags() to set the dir flags.
The user can update the direction and configuration
of each GPIO with a only call to dm_gpio_set_dir_flags() or
dm_gpio_set_dir() and respecting the configuration provided by
device tree (saved in desc->flags).

When these optional ops are absent, the gpio uclass use the mandatory
ops (direction_output, direction_input, get_value) and desc->flags
to manage only the main dir flags:
- GPIOD_IS_IN
- GPIOD_IS_OUT
- GPIOD_IS_OUT_ACTIVE
- GPIOD_ACTIVE_LOW

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/asm-generic/gpio.h

@@ -298,6 +298,22 @@ struct dm_gpio_ops {
 	int (*xlate)(struct udevice *dev, struct gpio_desc *desc,
 		     struct ofnode_phandle_args *args);
 
+	/**
+	 * set_dir_flags() - Set GPIO dir flags
+	 *
+	 * This function should set up the GPIO configuration according to the
+	 * information provide by the direction flags bitfield.
+	 *
+	 * This method is optional.
+	 *
+	 * @dev:	GPIO device
+	 * @offset:	GPIO offset within that device
+	 * @flags:	GPIO configuration to use
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*set_dir_flags)(struct udevice *dev, unsigned int offset,
+			     ulong flags);
+
 	/**
 	 * get_dir_flags() - Get GPIO dir flags
 	 *