rockchip: rk3399: Add Kconfig option for full pinctrl driver

This patch adds a Kconfig option to enable the full pinctrl driver
for the RK3399. This flag needs to be enabed in order to get the
features of the full pinctrl driver compiled in (i.e. a .set_state()
callback).

Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>