pinctrl: renesas: Protect GPIO leftovers by CONFIG_PINCTRL_SH_FUNC_GPIO

On SuperH and ARM SH/R-Mobile SoCs, the pin control driver handles
GPIOs, too.  To reduce code size when compiling a kernel supporting only
modern SoCs, most, but not all, of the GPIO functionality is protected
by checks for CONFIG_PINCTRL_SH_FUNC_GPIO.

Factor out the remaining parts when not needed:
  1. sh_pfc_soc_info.{in,out}put describe GPIO pins that have input
     resp. output capabilities (SuperH and SH/R-Mobile).
  2. sh_pfc_soc_info.gpio_irq{,_size} describe the mapping from GPIO
     pins to interrupt numbers (SH/R-Mobile).
  3. sh_pfc_gpio_set_direction() configures GPIO direction, called from
     the GPIO driver through pinctrl_gpio_direction_{in,out}put()
     (SH/R-Mobile).  Unfortunately this function cannot just be moved to
     drivers/pinctrl/renesas/gpio.c, as it relies on knowledge of
     sh_pfc_pinctrl, which is internal to
     drivers/pinctrl/renesas/pinctrl.c.

While code size reduction is minimal, this does help in documenting
depencies.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20201028151637.1734130-9-geert+renesas@glider.be