pinctrl: rockchip: remove unnecessary locking

regmap_update_bits does its own locking and everything else accessed
here is a local variable so there is no need to lock around it.

Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>