dt-bindings: pinctrl: mediatek: fix pinmux header location

Fix the location of the pinmux header files mentioned on the schemas.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230317213011.13656-17-arinc.unal@arinc9.com


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