gpio/rockchip: use struct rockchip_gpio_regs for gpio controller

Store register offsets in the struct rockchip_gpio_regs, this patch
prepare for the driver update for new gpio controller.

Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>
Link: https://lore.kernel.org/r/20210816012111.1119125-1-jay.xu@rock-chips.com


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