soc: nordic_nrf: Allow building with TF-M without platform partition

Allow building for nRF non-secure and TF-M enabled without having the
platform partition enabled.
In this configuration the soc_secure functions have no valid
implementation, leave it as a compilation error if the application
includes the functions.

Add missing dependency on soc_secure functions being available for
SOC_HFXO_CAP_INTERNAL configuration.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>