pinctrl: Ingenic: Add pinctrl driver for JZ4760 and JZ4760B.

Add support for probing the pinctrl-ingenic driver on the
JZ4760 Soc and the JZ4760B Soc from Ingenic.
Signed-off-by: Zhou Yanjie <zhouyanjie@zoho.com>
Link: https://lore.kernel.org/r/1563076436-5338-3-git-send-email-zhouyanjie@zoho.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>