pinctrl: mediatek: fix a memleak when do dt maps.

configs will kmemdup to dup_configs in pictrl util function.
So configs need to be freed.

Signed-off-by: Hongzhou Yang <hongzhou.yang@mediatek.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>