cmake: Minor refactoring of 'import_kconfig'
cmake: Minor refactoring of 'import_kconfig'

Minor refactoring of 'import_kconfig' in preparation of resolving

Signed-off-by: Sebastian Bøe <edee888afd63e94916688495334700803eba20a0@nordicsemi.no>

GiulianoFranchetto/zephyr,punitvara/zephyr,explora26/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,ldts/zephyr,finikorg/zephyr,nashif/zephyr,explora26/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,ldts/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,punitvara/zephyr,explora26/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,ldts/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr