pinctrl: mediatek: use devm_platform_ioremap_resource() to simplify code

Use devm_platform_ioremap_resource() to simplify the code a bit.
This is detected by coccinelle.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20191016141053.23740-1-yuehaibing@huawei.com


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