samples: tfm_integration: support TF-M samples on nRF5340 DK

Add support for nRF5340 DK in the TF-M integration
samples (nrf5340dk_nrf5340_cpuappns build target).
Add the required DTS overlays needed for the samples
to build and run successfully.

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