pinctrl: Ingenic: Add pinctrl driver for JZ4730.

Add support for probing the pinctrl-ingenic driver on the
JZ4730 SoC from Ingenic.

This driver is derived from Paul Boddie. It is worth to
noting that the JZ4730 SoC is special in having two control
registers (upper/lower), so add code to handle the JZ4730
specific register offsets and some register pairs which have
2 bits for each GPIO pin.

Tested-by: H. Nikolaus Schaller <hns@goldelico.com>  # on Letux400
Co-developed-by: Paul Boddie <paul@boddie.org.uk>
Signed-off-by: Paul Boddie <paul@boddie.org.uk>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/1618757073-1724-9-git-send-email-zhouyanjie@wanyeetech.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>