pinctrl/lantiq: add missing pin definition to falcon pinctrl driver

The pps pin definition is missing in the current code.

Signed-off-by: Thomas Langer <thomas.langer@lantiq.com>
Acked-by: John Crispin <blogic@openwrt.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>