gpio: brcmstb: add support for gpio-ranges

A pin controller device mapped with the gpio-ranges property
will need implementations of the .request and .free members of
the gpiochip.

Signed-off-by: Doug Berger <opendmb@gmail.com>
Tested-by: Phil Elwell <phil@raspberrypi.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20240424185039.1707812-4-opendmb@gmail.com


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>