gpio: Add ROHM BD9571MWV-M PMIC GPIO driver

Add driver for the GPIO block in the ROHM BD9571MWV-W MFD PMIC.
This block is pretty trivial and supports setting GPIO direction
as Input/Output and in case of Output, supports setting value.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: linux-gpio@vger.kernel.org
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>