cosmetic: rockchip: rk3288: pinctrl: fix config symbol naming

Revise config to CONFIG_ROCKCHIP_RK3288_PINCTRL.

Signed-off-by: Ziyuan Xu <jk.kernel@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>