[nrf fromtree] boards: Add secondary_app_partition alias#3309

nordicjm merged 1 commit intonrfconnect:mainnrfconnect/sdk-zephyr:mainfrom

tomchy:feature/mcuboot/NCSDK-35612_Dedicated_secondary_app_partitiontomchy/sdk-zephyr:feature/mcuboot/NCSDK-35612_Dedicated_secondary_app_partitionCopy head branch name to clipboard