pinctrl: renesas: add R906G032 driver

Pinctrl/pinconf driver for Renesas RZ/N1 (R906G032) SoC.

This is quite rudimentary right now, and only supports applying a
default pin configuration as specified by the device tree.

Signed-off-by: Ralph Siemsen <ralph.siemsen@linaro.org>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>