fs/nvs: preserve the previous ate searching

Previous ATE searching is accelerate by reading sector
close ate, which allow to skip reading whole storage.

ATE is already covered by crc8. That patch introduce
check on correctness offset read form close ate. This
increases meta-data integrity check level.
This also preserves against possible looping when read
incorrect or not a NVS storage image.

fixes #16899

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>