pinctrl: pinctrl-microchip-sgpio: Add irq support (for sparx5)

This adds 'interrupt-controller' features for the signals available on
the Microchip SGPIO controller, however only for controller versions
on the Sparx5 platform (or later).

Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Link: https://lore.kernel.org/r/20201209142753.683208-2-lars.povlsen@microchip.com


[Select GPIOLIB_IRQCHIP in Kconfig]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>