sh-pfc: Shrink the pinctrl GPIO range to include real GPIOs only

As a step towards GPIO function removal, shorten the GPIO range
registered with the pinctrl core. Function GPIOs are now handled in the
GPIO handlers directly instead of going through the pinctrl API.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>