platform: nordic_nrf: Move define to common CMake

Move NRF_NS_SECONDARY define to common CMake.

This improves portability.

Change-Id: Ie6dfff1b89cedfbc4bec93088c7d6f6e190a6f69
Signed-off-by: Markus Swarowsky <markus.swarowsky@nordicsemi.no>
3 files changed