The pins from GPIO1A0 to GPIO1B1 are special, need to recalculate
iomux. And the register offset is larger than the u8 range, so changed
to u32.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>