soc: nordic: nrf53: Forward gpio pins to network core just before reset

Instead of forwarding pins to the network core during the
initialization, do it just before reseting the network core. With
this approach pins can be used by the application core as long as
network core is not started.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>