pinctrl: Move Airoha driver to dedicated directory

pinctrl: Move Airoha driver to dedicated directory

In preparation for additional SoC support, move the Airoha pinctrl driver
for AN7581 SoC to a dedicated directory.

This is to tidy things up and keep code organized without polluting the
Mediatek driver directory.

The driver doesn't depend on any generic or common code from the Mediatek
codebase so it can be safely moved without any modification.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Linus Walleij <linusw@kernel.org>