gpio: 74x164: Introduce 'enable-gpios' property

      1 = active low

- registers-number: Number of daisy-chained shift registers

Optional properties:

- enable-gpios: GPIO connected to the OE (Output Enable) pin.

Example:

gpio5: gpio5@0 {

 *  published by the Free Software Foundation.

 */

#include <linux/gpio/consumer.h>

#include <linux/init.h>

#include <linux/mutex.h>

#include <linux/spi/spi.h>

	 * numbering, store the bytes in reverse order.

	 */

	u8			buffer[0];

	struct gpio_desc	*gpiod_oe;

};

static int __gen_74x164_write_config(struct gen_74x164_chip *chip)

	if (!chip)

		return -ENOMEM;

	chip->gpiod_oe = devm_gpiod_get_optional(&spi->dev, "enable",

						 GPIOD_OUT_LOW);

	if (IS_ERR(chip->gpiod_oe))

		return PTR_ERR(chip->gpiod_oe);

	gpiod_set_value_cansleep(chip->gpiod_oe, 1);

	spi_set_drvdata(spi, chip);

	chip->gpio_chip.label = spi->modalias;

{

	struct gen_74x164_chip *chip = spi_get_drvdata(spi);

	gpiod_set_value_cansleep(chip->gpiod_oe, 0);

	gpiochip_remove(&chip->gpio_chip);

	mutex_destroy(&chip->lock);