modules: hal_nordic: Set SOC_SVD_FILE

This CMake variable contains a path to a CMSIS-SVD file from nRF MDK,
which describes the selected Nordic SoC.

Initially, this will be used as an argument to nrf-regtool.

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>