gpio: pca9570: add GPO driver for PCA9570

NXP PCA9570 is a 4-bit I2C GPO expander without interrupt functionality.
Its ports are controlled only by a data byte without register address.

Signed-off-by: Sungbo Eo <mans0n@gorani.run>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Datasheet: https://www.nxp.com/docs/en/data-sheet/PCA9570.pdf
Link: https://lore.kernel.org/r/20200709134829.216393-1-mans0n@gorani.run


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>