pinctrl: visconti: Add Toshiba Visconti SoCs pinctrl support

Add pinctrl support to Toshiba Visconti SoCs.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Reviewed-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
Link: https://lore.kernel.org/r/20200909204336.2558-3-nobuhiro1.iwamatsu@toshiba.co.jp
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>