boards: arm: nrf5340_dk: fix nRF Cache and NVMC macro usage

We need to fix the formato of the macros for nRF CACHE and NVMC
peripherals in soc.c, so the _S and _NS suffixes are skipped.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>