[Backport ncs-v3.1-branch] [nrf noup] boot: zephyr: remove nonsecure ram cleanup#516

rlubos merged 1 commit intoncs-v3.1-branchnrfconnect/sdk-mcuboot:ncs-v3.1-branchfrom

backport-514-to-ncs-v3.1-branchnrfconnect/sdk-mcuboot:backport-514-to-ncs-v3.1-branchCopy head branch name to clipboard