pinctrl: mediatek: mtk-common: Use devm_kcalloc at appropriate places

Prefer devm_kcalloc over devm_kzalloc with multiply.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Hongzhou Yang <hongzhou.yang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>