pinctrl: pinctrl-microchip-sgpio: Add OF config dependency

The pinctrl-microchip-sgpio driver needs OF support, so add that to
Kconfig.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20201125122014.11237-1-lars.povlsen@microchip.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>