platform: nordic_nrf: Move STORAGE define to common CMake

Move NRF_NS_STORAGE define to a common CMake file.

This improves portability.

Signed-off-by: Markus Swarowsky <markus.swarowsky@nordicsemi.no>
Change-Id: I1fc57f58b507222a0927a9688d56c55549d5dcfa
4 files changed