pinctrl: sh-pfc: Stop calling gpiochip_add_pin_range() on DT platforms

On platforms where the PFC/GPIO controller is instantiated from DT, the
mapping between GPIOs and pins is set up using the "gpio-ranges"
property in DT.

Hence stop setting up the mapping from C code on DT platforms.
This code is still used for SH or ARM-legacy platforms.

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