boards: arm: Add support for TF-M in nRF9160 DK

Adding support for TF-M in the Nordic nRF9160 DK.
Allow the TF-M integration samples to be built and
executed for nRF9160 DK.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
6 files changed