gpio: mpfs: add polarfire soc gpio support

gpio: mpfs: add polarfire soc gpio support

Add a driver to support the Polarfire SoC gpio controller. Interrupt
controller support is unavailable for now and will be added at a later
date.

Signed-off-by: Lewis Hanly <lewis.hanly@microchip.com>
Co-developed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20241104-tiny-evaluate-9336020b4b6a@spud
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>