pinctrl: ingenic: jz4730: add pinmux for MII

The MII interface is used for the Ethernet connection of the Alpha400.

Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Link: https://lore.kernel.org/972b31e1fce03808745e53df17315b29e2bcf696.1740823241.git.hns@goldelico.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>