pinctrl: mediatek: fix naming inconsistency

Some options include "MediaTek", some "Mediatek". Rename all to "MediaTek"
to address the naming inconsistency.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/20230218065108.8958-2-arinc.unal@arinc9.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>