gpio: bd71828: Initial support for ROHM BD71828 PMIC GPIOs

ROHM BD71828 PMIC contains 4 pins which can be configured by OTP
to be used for general purposes. First 3 can be used as outputs
and 4.th pin can be used as input. Allow them to be controlled
via GPIO framework.

The driver assumes all of the pins are configured as GPIOs and
trusts that the reserved pins in other OTP configurations are
excluded from control using "gpio-reserved-ranges" device tree
property (or left untouched by GPIO users).

Typical use for 4.th pin (input) is to use it as HALL sensor
input so that this pin state is toggled when HALL sensor detects
LID position change (from close to open or open to close). PMIC
HW implements some extra logic which allows PMIC to power-up the
system when this pin is toggled. Please see the data sheet for
details of GPIO options which can be selected by OTP settings.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>