pinctrl: renesas: gpio: Use dynamic GPIO base if no function GPIOs

Since commit 502df79b ("gpiolib: Warn on drivers still using
static gpiobase allocation") in gpio/for-next, one or more warnings are
printed during boot on systems where the pin controller also provides
GPIO functionality:

    gpio gpiochip0: Static allocation of GPIO base is deprecated, use dynamic allocation.

Fix this for ARM-based SH/R-Mobile SoCs by:
  1. Taking into account a non-zero GPIO base in the various GPIO chip
     callbacks,
  2. Switching to dynamic allocation of the GPIO base when support for
     legacy function GPIOs is not enabled.

On SuperH SoCs using legacy function GPIOs, the GPIO bases of the GPIO
controller and the GPIO function controller must not be changed, as all
board files rely on the fixed GPIO_* and GPIO_FN_* definitions provided
by the various <cpu/sh*.h> header files.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/df2cf30ac4c3cbee726799f32b727c1ebe62819c.1668000684.git.geert+renesas@glider.be