NRF_UICR needs to be defined for nRF9160 SoC in nrfx_config_nrf9160.h, because it is not defined in nrfx/hal/mdk/nrf9160.h (as it is a Secure-only peripheral). Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>