hal_nordic: ironside: Add 9251 peripherals

- Add Fast and Slow peripherals controlled through
Ctrlsel and PSel configuration.

- Certain choices have been made in case of multiple
peripherals using the same port, this is done in respect
of nrf9251pdk_nrf9251-pinctrl.dtsi content.

Signed-off-by: Aymen LAOUINI <aymen.laouini@nordicsemi.no>

Author: ayla-nordicsemi