sh-pfc: Don't define the per-device pinctrl struct instances as global

The pinctrl_desc and pinctrl_gpio_range structures registered with the
pinctrl core are per-device instances. Move them to the dynamically
allocated sh_pfc_pinctrl structure and initialize them at runtime.

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