ARM: rockchip: Kconfig: Remove the SPL_PINCTRL for rk3188

It seems that pinctrl is not requested for rk3188 SPL, remove it so
that can save more space for SPL image size.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>